The elbow: review of anatomy and common collateral ligament complex pathology using MRI

Artificial intelligence powered advancements in upper extremity joint MRI: A review

Magnetic resonance imaging (MRI) is an indispensable medical imaging examination technique in musculoskeletal medicine. Modern MRI techniques achieve superior high-quality multiplanar imaging of soft tissue and skeletal pathologies without the harmful effects of ionizing radiation. Some current limitations of MRI include long acquisition times, artifacts, and noise. In addition, it is often challenging to distinguish abutting or closely applied soft tissue structures with similar signal characteristics. In the past decade, Artificial Intelligence (AI) has been widely employed in musculoskeletal MRI to help reduce the image acquisition time and improve image quality. Apart from being able to reduce medical costs, AI can assist clinicians in diagnosing diseases more accurately. This will effectively help formulate appropriate treatment plans and ultimately improve patient care. This review article intends to summarize AI's current research and application in musculoskeletal MRI, particularly the advancement of DL in identifying the structure and lesions of upper extremity joints in MRI images.

Flexed elbow, abducted shoulder, forearm supinated (FABS) reconstruction from three-dimensional elbow MRI: diagnostic performance assessment in biceps head anatomy and pathology

AIM

To determine inter-reader analysis and diagnostic performance on digitally reconstructed virtual flexed, abducted, supinated (FABS) imaging from three-dimensional (3D) isotropic elbow magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Six musculoskeletal radiologists independently evaluated elbow MRI images with virtual FABS reconstructions, blinded to clinical findings and final diagnoses. Each radiologist recorded a binary result as to whether the tendon was intact and if both heads were visible, along with a categorical value to the type of tear and extent of retraction in centimetres where applicable. Kappa and interclass correlation (ICC) were reported with 95% confidence intervals. Areas under the receiver operating curve (AUC) were reported.

RESULTS

FABS reconstructions were obtained successfully in all 48 cases. With respect to tendon intactness, visibility of both heads, and type of tear, the Kappa values were 0.66 (0.53-0.78), 0.24 (0.12-0.37), and 0.55 (0.43-0.66), respectively. For the extent of retraction, the ICC was 0.85 (0.79-0.91) when including the tendons with and without retraction and 0.78 (0.61-0.91) when only including tendons with retraction. For tear versus no tear, AUC values were 0.82 (0.74-0.89) to 0.96 (0.91-1.01).

CONCLUSION

Digital reconstruction of FABS positioning is feasible and allows good assessment of individual tendon head tears and retraction with high diagnostic performance.

Current concepts in the management of "Terrible Triad" injuries of the elbow

Terrible triad injuries of the elbow are complex injuries which can result in long term complications and significant disability. They must be identified correctly, and managed appropriately in order to maximise functional outcomes. A clear understanding of the bony and ligamentous anatomy is essential to plan appropriate surgical reconstruction to provide elbow stability. Urgent reduction of the elbow, followed by 3-dimensional imaging and surgical repair or replacement of the injured structures is the mainstay of treatment in the majority of cases. This review presents a summary of the relevant anatomy and the evidence for the management of these complex injuries.

Imaging of Anatomical Variants Around the Elbow

The elbow is a synovial joint able to perform flexion, extension, supination, and pronation. Knowledge of anatomical variants is crucial to avoid misinterpretation during the evaluation of the elbow joint. We address those anatomical variants simulating pathologic conditions.

Knuckle-walking in Sahelanthropus? Locomotor inferences from the ulnae of fossil hominins and other hominoids

Because the ulna supports and transmits forces during movement, its morphology can signal aspects of functional adaptation. To test whether, like extant apes, some hominins habitually recruit the forelimb in locomotion, we separate the ulna shaft and ulna proximal complex for independent shape analyses via elliptical Fourier methods to identify functional signals. We examine the relative influence of locomotion, taxonomy, and body mass on ulna contours in Homo sapiens (n = 22), five species of extant apes (n = 33), two Miocene apes (Hispanopithecus and Danuvius), and 17 fossil hominin specimens including Sahelanthropus, Ardipithecus, Australopithecus, Paranthropus, and early Homo. Ulna proximal complex contours correlate with body mass but not locomotor patterns, while ulna shafts significantly correlate with locomotion. African apes' ulna shafts are more robust and curved than Asian apes and are unlike other terrestrial mammals (including other primates), curving ventrally rather than dorsally. Because this distinctive curvature is absent in orangutans and hylobatids, it is likely a function of powerful flexors engaged in wrist and hand stabilization during knuckle-walking, and not an adaptation to climbing or suspensory behavior. The OH 36 (purported Paranthropus boisei) and TM 266 (assigned to Sahelanthropus tchadensis) fossils differ from other hominins by falling within the knuckle-walking morphospace, and thus appear to show forelimb morphology consistent with terrestrial locomotion. Discriminant function analysis classifies both OH 36 and TM 266 with Pan and Gorilla with high posterior probability. Along with its associated femur, the TM 266 ulna shaft contours and its deep, keeled trochlear notch comprise a suite of traits signaling African ape-like quadrupedalism. While implications for the phylogenetic position and hominin status of S. tchadensis remain equivocal, this study supports the growing body of evidence indicating that S. tchadensis was not an obligate biped, but instead represents a late Miocene hominid with knuckle-walking adaptations.

The sonographic posterolateral rotatory stress test: Normal ulnohumeral gap difference in healthy volunteers

Background: The sonographic posterolateral rotatory stress test may be a good preoperative diagnostic tool for posterolateral rotatory instability, especially in atraumatic or occult cases. However, there is lack of study on the living population or the normal elbow. Hypothesis/Purpose: This study evaluates the ulnohumeral opening gap difference between elbows in resting and stress positions while performing ultrasonography in normal healthy volunteers. The hypothesis is that the normal ulnohumeral opening gap difference is less than 2 mm. Methods: A total of 21 participants (9 males and 12 females) who presented at our institution between May and June 2021 were recruited. First, participants with elbow deformity, major elbow trauma, history of injection or surgery around the elbow, or evidence of elbow instability were excluded. Only healthy elbows without symptoms were included in this study. Participants' both elbows were examined using ultrasonography. The ulnohumeral gap was measured in millimeters, and the difference was calculated from the means of ulnohumeral gap in resting and stress positions. Results: The mean age of participants was 36.14 years old. No samples with hyperlaxity were included. Overall, the means of ulnohumeral gap in resting and stress positions were 2.55 ± 0.69 mm and 3.16 ± 0.80 mm, respectively. The average mean of overall ulnohumeral opening gap difference was 0.61 ± 0.32 mm. There was no statistically significant difference between males and females (p = .989). The intraobserver reliability was 0.89 and 0.9 for resting and stress positions, respectively. Conclusion: The sonographic posterolateral rotatory stress test shows that the ulnohumeral opening gap difference between resting and stress positions is less than 2 mm in healthy volunteers. Clinical Relevance: In patients with inconclusively-diagnosed PLRI, the sonographic posterolateral rotatory stress test may be a reliable preoperative diagnosis tool, providing its non-invasiveness and the ability to assess the contralateral side as a comparison.

Acute combined collateral ligaments injury of the elbow without any fracture or dislocation-a case report

Introduction

The combination of both collateral ligaments injury in the elbow without fractures or dislocations is not reported in the literature.

Case presentation

a case report of rare acute combined collateral ligaments injury of the elbow was treated surgically by repairing both collateral ligament complexes with two different approaches.

Clinical discussion

Clinical examination at 3 months showed a stable elbow with a flexion arc from 0 to 140. 10 degrees residual varus laxity was observed.

Pronation and supination were unrestricted. The patient experienced mild pain and was able to do push up and was completely satisfied with the result.

Conclusion

The case presented is the first case presented in the literature with acute combined and isolated collateral ligaments injury of the elbow. Based on the clinical result obtained. We propose acute surgical approach of both collateral ligaments for such types of injury.

Level of evidence: 4.

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The combination of both collateral ligaments injury in the elbow without fractures or dislocations is not reported in the literature.

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Primary ligament repair followed by an early mobilisation programme to treat unstable elbow provided satisfactory functional results, range of motion and stability.

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Anatomical restoration of the soft tissue stabiliser of the elbow joint is important in such types of unstable elbow in order to avoid a complicated secondary reconstruction procedure.

TREATMENT OF SIMPLE CHRONIC INSTABILITY OF THE ELBOW JOINT

Simple chronic instability of the elbow joint is one of the urgent problems in modern traumatology due to the fact that the standard tactics of managing patients with traumatic injuries of the elbow joint due to dislocation, which amounts to its elimination, immobilization of the upper limb and subsequent development of movements in the joint, most often does not take into account damage to specific soft tissue structures. With untimely treatment for qualified help, with late or unsuccessful attempts to eliminate dislocation of the bones of the forearm, less often with chronic traumatization of the ligamentous apparatus of the elbow joint during some types of occupation, one of the most unpleasant complications may form, namely, chronic instability. This article discusses the main types of chronic instability of the elbow joint, analyzes approaches to the management of patients with simple chronic instability. Despite the not very high occurrence of this pathology, the effectiveness of modern surgical treatment options aimed at reconstruction of the ligamentous apparatus of the elbow joint, the percentage of unsatisfactory results of treatment of simple chronic recurrent and persistent instability of the elbow joint remains high.

MRI of the Elbow: Interpretation of Common Orthopaedic Injuries

MRI is a valuable diagnostic tool that has become an essential part of an orthopaedic surgeon's practice. When acquired in the appropriate clinical setting, an MRI can direct patient management as surgical versus nonsurgical, guide surgical decision making, and even predict patient outcomes. The quality of MRI obtained and quality of the radiology report received varies. Ultimately, the orthopaedic surgeon must interpret the available imaging and apply these findings to treat the patient. The current day practicing orthopaedic surgeon should be familiar with interpreting common MRIs. Although subspecialized orthopaedic surgeons usually have experience and understanding of MRIs in their field, the general orthopaedic surgeon and those in-training will encounter the gamut of musculoskeletal MRIs. This review focuses on common injuries that can occur in the elbow and provides an approach to minimize missed findings.

LUCL reconstruction of the elbow: clinical midterm results based on the underlying pathogenesis

PURPOSE

Traumatic and atraumatic insufficiency of the lateral ulnar collateral ligament (LUCL) can cause posterolateral rotatory instability (PLRI) of the elbow. The influence of the underlying pathogenesis on functional outcomes remains unknown so far. The objective of this study was to determine the impact of the initial pathogenesis of PLRI on clinical outcomes after LUCL reconstruction using an ipsilateral triceps tendon autograft.

METHODS

Thirty-six patients were reviewed in this retrospective study. Depending on the pathogenesis patients were assigned to either group EPI (atraumatic, secondary LUCL insufficiency due to chronic epicondylopathia) or group TRAUMA (traumatic LUCL lesion). Range-of-motion (ROM) and posterolateral joint stability were evaluated preoperatively and at follow-up survey. For clinical assessment, the Mayo elbow performance (MEPS) score was used. Patient-reported outcomes (PROs) consisting of visual analogue scale (VAS) for pain, disability of arm, shoulder and hand (DASH) score, patient-rated elbow evaluation (PREE) score and subjective elbow evaluation (SEV) as well as complications were analyzed.

RESULTS

Thirty-one patients (group EPI, n = 17; group TRAUMA, n = 14), 13 men and 18 women with a mean age of 42.9 ± 11.0 were available for follow-up evaluation (57.7 ± 17.5 months). In 93.5%, posterolateral elbow stability was restored (n = 2 with re-instability, both group TRAUMA). No differences were seen between groups in relation to ROM. Even though group EPI (98.9 ± 3.7 points) showed better results than group TRAUMA (91.1 ± 12.6 points) (p = 0.034) according to MEPS, no differences were found for evaluated PROs (group A: VAS 1 ± 1.8, PREE 9.3 ± 15.7, DASH 7.7 ± 11.9, SEV 92.9 ± 8.3 vs. group B: VAS 1.9 ± 3.2, PREE 22.4 ± 26.1, DASH 16.0 ± 19.4, SEV 87.9 ± 15.4. 12.9% of patients required revision surgery.

CONCLUSION

LUCL reconstruction using a triceps tendon autograft for the treatment of PLRI provides good to excellent clinical outcomes regardless of the underlying pathogenesis (traumatic vs. atraumatic). However, in the present case series, posterolateral re-instability tends to be higher for traumatic PLRI and patient-reported outcomes showed inferior results.

LEVEL OF EVIDENCE

Therapeutic study, LEVEL III.

Elbow Imaging: Variants and Asymptomatic Findings

One of the key principles in the interpretation of radiology images is the ability to differentiate between normal and abnormal findings. This article provides a comprehensive overview of normal structures and anatomical variants occurring around the elbow including potential diagnostic pitfalls. We discuss frequently observed anatomical variants found in routine clinical practice associated with osseous, ligamentous, musculotendinous, and neurovascular structures at the elbow that may simulate pathology or predispose to symptoms under specific circumstances.

Posteromedial rotatory instability of the elbow: What the radiologist needs to know

Varus posteromedial rotatory instability of the elbow joint is a relatively new subject described for the first time in 2003. It occurs secondary to axial loading of the elbow with varus force and internal rotation of the forearm. There is usually a specific pattern of osseous and soft tissue injuries that can be recognized on imaging. This includes an anteromedial coronoid fracture and avulsion of the lateral collateral ligament complex from its humeral attachment. Ulnar collateral ligament complex injury is also reported, particularly its posterior bundle which plays an important role in posteromedial elbow joint stability. There is high incidence of early osteoarthritis secondary to the resultant varus instability and increased contact pressure at the ulnohumeral joint. Surgical fixation of the coronoid fracture and ligamentous reconstruction maybe indicated to prevent this recurrent instability. The article reviews the key radiological features of posteromedial rotatory instability with multiple examples from different imaging modalities. The relevant anatomy of the elbow joint stabilising structures will be illustrated, in particular the coronoid process anatomy and the O'Driscoll classification for coronoid process fractures. Radiologists should be familiar with the imaging findings of posteromedial rotatory instability.

Does sonography allow an objective and reproducible distinction between stable, hypermobile, and unstable elbow joints?

BACKGROUND

The diagnosis of residual or chronic elbow instability is often challenging. Sonography allows a dynamic examination of the elbow joint without any radiation exposure. The purpose of this prospective single-center study was to investigate the application of sonography for the evaluation of ligamentous instabilities of the elbow joint. Therefore, asymptomatic (stable) and acute dislocated (unstable) elbows were examined by sonography.

METHODS

A total of 72 elbows in 36 participants (23 women and 13 men; mean age, 40 ± 17 years [range, 18-82 years]) were examined. Group 1 (G1 [normal]) included 40 unaffected, asymptomatic elbow joints; 28 elbows belonged to 14 voluntary participants (bilateral), whereas 12 asymptomatic elbows belonged to patients who had an acute elbow dislocation (contralateral elbow). Group 2 (G2 [hypermobile]) included 20 hypermobile elbow joints in 10 participants (bilateral), and group 3 (G3 [unstable]) included 12 acute unstable elbow joints without bony lesions. Radiographic assessment included sonography of both elbow joints with standardized measurements of the neutral and stressed radiocapitellar and ulnohumeral distances (calculated as Δ values). Two investigators independently performed all measurements. Additionally, plain radiographs and magnetic resonance imaging of the affected elbow joints were obtained in G3.

RESULTS

On the radial side, the mean radiocapitellar Δ was statistically higher in G3 (2.2 ± 1.6 mm) than in G1 (0.5 ± 0.4 mm, P < .01) or G2 (0.8 ± 0.6 mm, P < .01). G3 also showed an increased ulnohumeral Δ (2.7 ± 0.7 mm) compared with G1 (1.0 ± 0.7 mm, P < .01) or G2 (0.9 ± 0.3 mm, P < .01). No significant differences in the mean radiocapitellar Δ (P = .06) and ulnohumeral Δ (P = .26) were found between G1 and G2. Within G3, Δ was significantly higher at the affected elbow joint than at the contralateral, unaffected elbow joint (P = .04 for the radial side and P = .04 for the ulnar side). The inter-rater correlation coefficient was 0.82 for the radial side and 0.74 for the ulnar side. Patients with collateral ligament injuries, diagnosed on magnetic resonance imaging, showed higher Δ values than those with intact collateral ligaments, although no significant difference was found.

CONCLUSION

Sonography of the elbow joint is a valuable imaging tool for the assessment of ligamentous instability. Nevertheless, a distinction between healthy and hypermobile elbow joints is not possible, and therefore, obtaining a complete clinical history and examination is vital. We further recommend comparing the affected elbow joint with the contralateral side to access intraindividual differences.

Evaluation and management of elbow injuries in the adolescent overhead athlete

With an increased interest in youth sports, the burden of overhead throwing elbow injuries accompanying early single-sport focus has steadily risen. During the overhead throwing motion, valgus torque can reach and surpass Newton meters (N m) during the late cocking and early acceleration phases, which exceeds the tensile strength (22.7–33 N m) of the ulnar collateral ligament. While the ulnar collateral ligament serves as the primary valgus stabilizer between and degrees of elbow flexion, other structures about the elbow must contribute to stability during throwing. Depending on an athlete’s stage of skeletal maturity, certain patterns of injury are observed with mechanical failures resulting from increased medial laxity, lateral-sided compression, and posterior extension shearing forces. Together, these injury patterns represent a wide range of conditions that arise from valgus extension overload. The purpose of this article is to review common pathologies observed in the adolescent overhead throwing athlete in the context of functional anatomy, osseous development, and throwing mechanics. Operative and non-operative management and their associated outcomes will be discussed for these injuries.

Hidden instability in posttraumatic stiff elbows

BACKGROUND

Hidden instability could be one of the reasons for reoccurring stiffness after arthrolysis in posttraumatic elbows. Associated instability in stiff posttraumatic elbows is clinically hard to detect. Surgical treatment for instability and stiffness in the same surgical setting is challenging and has not been evaluated as of yet.

HYPOTHESIS

The primary hypothesis assumes (1) the existence of a posttraumatic "stiff and unstable elbow" and (2) that coexisting instability can be detected by arthroscopic instability testing. The secondary objective was to report the midterm results after arthrolysis and ligament stabilization in the stiff and unstable elbow.

METHODS

From 2005 to 2015, 55 patients received arthroscopic arthrolysis of the elbow due to posttraumatic elbow stiffness at our institution. The arthroscopic instability was categorized into three grades with a switching stick: grade I (= stable), grade II (mild instability) and grade III (grossly instable). In cases of persisting instability (grade II-III), a ligament stabilization procedure was performed and all patients were followed up clinically at a minimum of 12 months. Besides ROM and clinical joint stability, PROs (patient reported outcomes) were assessed with the PREE-score (patient-rated elbow evaluation) and the Oxford-Elbow-score (OES). Furthermore, the MEPS (Mayo-elbow-performance-score) was assessed.

RESULTS

Out of 55 cases presenting for arthrolysis, coexisting elbow instability was detected during arthroscopic instability testing in 22 cases (40%). All 22 patients received additional ligament stabilization. At final follow-up 62.7 ± 35.7 months postoperatively, 20 patients (12 men; 8 women) with a mean age of 42 ± 16.8 were available. PREE, OES and MEPS were 19.8 ± 25.3, 37.5 ± 9.8 and 80 ± 14.5, respectively. ROM improved significantly from 95° ± 29° to 110° ± 24° postoperatively (p = 0.045). Five patients required revision arthrolysis within the follow-up period (20%). One patient demonstrated persisting instability (5%).

CONCLUSION

Intraoperative instability diagnostics during arthroscopic arthrolysis helps detect persisting posttraumatic instability and may provide a solid indication for a concurrent ligament stabilization procedure. This study is the first to present the postoperative results after arthrolysis with stabilization of the posttraumatic, stiff and unstable elbow. However, the results are heterogenic with 25% requiring revision arthrolysis. Therefore, the stiff but unstable elbow remains a complex clinical presentation in need of further investigations.

LEVEL OF EVIDENCE

IV.

MRI in acute simple elbow dislocations: correlation of preoperative imaging and intraoperative findings of collateral ligaments and associated soft tissue injuries

PURPOSE

The aim of our study was the evaluation of correspondence among collateral ligaments and other soft tissue injuries detected by MRI and by intraoperative findings in a consecutive series of patients treated for simple elbow dislocation.

METHODS

After clinical and MRI examination, 16 out of 59 consecutive patients with moderate or severe instability after simple elbow dislocation were addressed to surgical treatment. There were 14 men and 2 women. The mean age was 39.6 years (range 16-69 years).

RESULTS

MRI showed full-thickness lesion of MCL in 9/16 patients (53.3%) and partial lesion in 6/16 patients (40%), and in 1 case, the MCL was considered intact. On the lateral side, MRI showed complete injury of LCL in 7/16 patients (46.6%) and partial injury in 7/16 patients (40%). No lesions of LCL were observed in 2 patients (13.4%). MCL was surgically explored in all the patients. We observed 10/16 full-thickness lesions (62.5%) and 6/16 partial lesions (37.5%). LCL was surgically explored in 11/16 patients. We observed 6/11 full-thickness lesions (54.6%) and 5/11 partial lesions (45.4%). In 3 cases, associated soft tissue injuries were detected. The rate of concordance between MRI and surgical findings was 87.5% (14/16 cases) on the medial side and 90.9% (10/11 cases) on the lateral side.

CONCLUSION

Our study demonstrated that MRI is a reliable and useful tool to investigate collateral ligaments and soft tissue injuries around the elbow and to plan the most adequate surgical treatment.

Isolated displaced type II partial articular radial head fracture: correlation of preoperative imaging with intraoperative findings of lateral ulnar collateral ligament tear

BACKGROUND

The aim of this study was to determine the lateral ulnar collateral ligament (LUCL) injury associated with isolated radial head fracture (RHF) and the relationship of the ligament injury with the displacement of the fragment-loss of contact-in unstable displaced partial articular RHF in individuals without any history of ulnohumeral dislocation.

METHODS

We retrospectively identified 131 consecutive patients who underwent open reduction and internal fixation of isolated closed Mason type II RHF performed at our institution. We identified 3 subsets by the pattern of RHF and the position of the unstable fragment (anterior or posterior) relative to the capitulum humeri: displaced stable (group I), displaced anterior unstable (group II), and displaced posterior unstable (group III). Standard radiographs were obtained preoperatively and postoperatively. The pattern of lateral collateral ligament avulsion and its distribution were inferred from intraoperative records.

RESULTS

Preoperative radiographs of the 131 patients showed 101 nonseparated fractures (77%, group I) and 30 unstable fractures (23%). Anterior displacement of the fragment was found in 18 elbows (14%, group II) and posterior displacement in 12 (9%, group III). LUCL avulsion was found in 18 of 30 unstable RHFs (60%) and in 1 of 60 stable RHFs (1.6%).

CONCLUSION

RHF is a complex fracture often associated with soft tissue lesions. It is important to determine which structures need to be repaired to avoid complications that could lead to elbow instability. The RHF pattern and classification as stable or unstable can help the surgeon in the identification and treatment of LUCL lesions.