The anconeus, an active lateral ligament of the elbow: new anatomical arguments

Anconeus and pronation: a palpatory and ultrasonographic study

PURPOSE

Depending on its axis, pronation varies from the radius rotation around the steady ulna to the reciprocal adduction of the radius and abduction of the ulna. While there is no question that pronator teres is a central pronation agonist, anconeus's role is not settled. The current investigation comparing palpation and ultrasonography in these two muscles during pronation along the axis capitulum-second digit evolved from a serendipitous finding in a clinical anatomy seminar.

METHODS

Single-hand palpation and two-transducer ultrasonography over anconeus and pronator teres were used on ten normal subjects to investigate their contraction during pronation around the capitulum-second digit axis. These studies were done independently and blind to the results of the other. The statistical analysis between palpation and ultrasonography was performed with Cohen's kappa coefficient and the χ2 test.

RESULTS

On palpation, on resisted full pronation, anconeus contracted in 8/10 subjects and pronator teres in 10/10 subjects. Without resistance, the corresponding ratios were 5/10 and 9/10. On two-transducer ultrasonography, the comparable ratios were 7/10 and 10/10, and 3/10 and 10/10. A fair concordance (Cohen's kappa = 0.21) between palpation and ultrasonography in detecting the simultaneous status of anconeus and pronator teres during resisted full pronation. Anatomic dissection illustrated the elements involved.

CONCLUSIONS

Plain palpation confirmed by ultrasonography showed the simultaneous contraction of anconeus and pronator teres during resisted pronation in most of the studied subjects. The study suggests that palpation can be helpful in directly studying muscle activity during movement.

Anconeus-sparing minimally invasive approach for lateral ulnar collateral ligament reconstruction using a triceps tendon autograft is an effective and safe treatment for chronic posterolateral instability of the elbow

BACKGROUND

Surgical treatment helps to restore stability of the elbow in patients with posterolateral rotatory instability (PLRI). The anconeus muscle is one of the most important active stabilizers against PLRI. A minimally invasive anconeus-sparing approach for lateral ulnar collateral ligament (LUCL) reconstruction using a triceps tendon autograft has been previously described. The purpose of this study was to evaluate the outcome of this intervention and identify risk factors that influenced the clinical and patient-reported outcomes.

METHODS

Sixty-one patients with chronic PLRI and no previous elbow surgery who underwent surgical reconstruction of the LUCL using a triceps tendon autograft in a minimally invasive anconeus-sparing approach during 2012 and 2018 were evaluated. Outcome measures included a clinical examination and the Oxford Elbow Score (OES) and the Mayo Elbow Performance Score (MEPS) questionnaires. Subjective patient outcomes were evaluated with the visual analog scale (VAS) for pain and the Subjective Elbow Value (SEV). Integrity of the common extensor tendons and centering of the radial head were assessed preoperatively on standardized magnetic resonance images (MRIs).

RESULTS

Fifty-two patients were available at final follow-up. The mean age of patients was 51 ± 12 years with a mean follow-up of 53 ± 14 months (range 20-76). Clinical examination after surgery (n = 41) showed no clinical signs of instability in 98% of the patients (P < .001) and a nonsignificant improvement in range of motion. OES, MEPS, and VAS scores averaged 40 ± 10 of 48 points, 92 ± 12 of 100 points, and 1 ± 2 points, respectively, all corresponding with good or excellent outcomes. The SEV was 88%, indicating very high satisfaction with the surgery. Only 1 patient had revision surgery due to pain, and there were no reported postoperative complications in this cohort. A radial head subluxation in the MRI correlated significantly with worse postoperative outcomes.

CONCLUSIONS

The anconeus-sparing minimally invasive technique for posterolateral stabilization of the elbow using a triceps tendon autograft is an effective and safe treatment for chronic posterolateral instability of the elbow with substantial improvements in elbow function and pain relief with a very low rate of persistent clinical instability.

The role of the lateral part of the distal triceps and the anconeus in varus stability of the elbow: a biomechanical study

BACKGROUND

The role of the lateral part of the distal triceps as a stabilizer in the lateral collateral ligament-deficient elbow and whether its effect in improving the stability is independent of that of the anconeus are unclear.

METHODS

Seven cadaveric elbows were tested under gravity varus stress using a custom-made machine designed to simulate muscle loads while allowing passive flexion of the elbow. An injury model was created by sectioning the lateral collateral ligament and sparing the common extensor origin. The lateral part of the distal triceps tendon was loaded sequentially with 0 N, 10 N, 25 N, and 40 N. Each stage of the lateral part of the distal triceps loading was tested with the anconeus unloaded (inactive) or with a 25-N load applied (active). Articular contact pressures on the coronoid, the medial facet, and the lateral facet were collected and processed using Tekscan sensors and software.

RESULTS

A significant decrease in the mean coronoid contact pressure was seen with sequential loading of the lateral part of the distal triceps (P < .001). The ratio of medial to lateral facet contact pressures significantly decreased with sequential loading of the lateral part of the distal triceps (P < .001), indicating a better distribution of the contact pressure between the medial and lateral facets as the lateral part of the distal triceps was loaded. These effects were statistically significant, both with and without anconeus loading. There was no significant modification of the effect of the lateral part of the distal triceps loading on the contact pressure by the anconeus loading (P = .47). However, with active anconeus loading, the contact pressure and the ratio of medial to lateral facet contact pressures were significantly lower for any stage of lateral triceps loading (P < .001), indicating a synergistic effect of the anconeus.

CONCLUSIONS

In a lateral collateral ligament-deficient elbow, the lateral part of the distal triceps loading prevents the increased contact pressure on the coronoid under varus stress and improves the distribution of contact pressures on the coronoid. Anconeus loading further decreases and improves the distribution of the contact pressures; however, its effect is independent of that of the lateral part of the distal triceps. These results substantiate a role of the lateral part of the distal triceps as a dynamic constraint against elbow varus and have clinical implications for prevention and rehabilitation of elbow instability.

Lateral para-olecranon approach: surgical guide and anatomical considerations to the anconeus branch: is there a nerve-free zone?

PURPOSE

In the last decades, total elbow arthroplasty, elbow osteosynthesis and revision surgery have been more popularized. The study aimed to assess the course of the anconeus branch of the radial nerve in relation to two variations of the lateral para-olecranon approach, considering iatrogenic nerve injuries.

METHODS

The study consisted of 120 upper extremities from 60 Thiel-embalmed human specimens. Two randomized versions of the lateral para-olecranon approach (centrally orientated: P1 and laterally orientated: P2) were performed. The olecranon and the intersection points to the anconeus branch of the radial nerve were determined as anatomical landmarks. The measurements were assessed by two independent observers. Differences were analyzed using the Student's t test; associations were computed with the Pearson correlation (r). An alpha of 0.05 (p) and a confidence interval of 95% were set.

RESULTS

The intersection points averaged 12.3 cm (SD 1.8, range 8.2-16.8) for P1 versus 5.5 cm (SD 1.4, range 3.0-9.2) for P2 (p ≤ 0.001). Statistically significantly higher values for male and longer humeral specimens were revealed (all values: p < 0.05). Comparison of left and right sides yielded no difference. Excellent inter-rater agreements were found (ICC = 0.902, range 0.860-0.921). A correlation was evaluated between the humeral length and the distances in both approaches (P1: r = 0.550, p < 0.001, P2: r = 0.669, p < 0.001).

CONCLUSION

The data presented here allow preservation of the anconeus branch. The P1 forms a potential advantage by owing a broader safe zone. Using the centrally orientated approach seems to provide adequate nerve protection during surgery for one of the motor branches for extension of the elbow joint and might result in improved postoperative benefits.

The anconeus muscle revisited: double innervation pattern and its clinical implications

PURPOSE

The aim of the present study is to describe in detail the morphology and innervation pattern of the anconeus muscle, bearing in mind clinical implications such as iatrogenic injuries during surgical elbow approaches.

METHODS

A cadaveric study was performed; 56 elbows from 28 formalin-fixed cadavers belonging to the Anatomy Department of Universidad Complutense of Madrid were dissected. The triceps-anconeus nerve was located and dissected. A second innervation to the anconeus muscle from a branch of the posterior interosseous nerve (PIN) was occasionally detected. Taking the lateral epicondyle as a landmark, the entry points of both nerves in the muscle were referenced, the triceps-anconeus nerve was referenced at 0°, 30°, 45°, 70° and 90° of elbow flexion, and the PIN branch at 0°.

RESULTS

Anconeus muscle was present in all specimens. The triceps-anconeus nerve was present in all of the dissected elbows. A branch from PIN to the anconeus muscle was present in 38 of the 54 elbows (70.4%). There were statistically significant differences in all measurements regarding the specimens' gender, being higher for men.

CONCLUSIONS

There is evidence of a high frequency of a double innervation pattern for the anconeus muscle: the main branch of triceps-anconeus muscle depending on the radial nerve, which is liable to being damaged during posterior elbow approaches, and a secondary branch depending on the PIN. There are very few references to this finding in Anatomical literature and none with such a large sample size.

Lateral ulnar collateral ligament (LUCL) reconstruction for the treatment of recalcitrant lateral epicondylitis of the elbow: a comparison with open débridement of the extensor origin

Background

Based on the controversy over whether the extensor tendon is the only lesion of lateral epicondylitis of the elbow and numerous reports of concomitant lateral collateral ligament involvement, potential damage to the lateral collateral ligament complex should be considered for the treatment.

Methods

About 25 elbows in 23 patients (débridement group) and 22 elbows in 20 patients (reconstruction group) who were diagnosed with lateral epicondylitis and had an average of 22 months of symptoms revealing anatomical lesion on MRI were included. The capitellum-sublime tubercle-radial head (CSR) angle was measured on both sides preoperatively, and the visual analog scale (VAS) and Mayo elbow performance score (MEPS) were measured over 12 months, postoperatively.

Results

The initial preoperative mean VAS was statistically significant with 4.6 in the débridement group and 6.5 in the reconstruction group (P < .05). Postoperative VAS was continuously decreased in both groups with no significant difference at each assessment period (P < .05) but showed more rapid improvement in the reconstruction group compared with the débridement group. For MEPS, the reconstruction group showed significant improvement during the follow-up periods, and at the final follow-up MEPS, 3 cases in the débridement group and 0 cases in the reconstruction group showed a poor result, which was considered as surgery failure. The CSR angle of the affected side (7.2 ± 1.9) was significantly larger than that of the normal side (3.6 ± 1.5) (P < .05) in the reconstruction group. Increased CSR by more than 5 degrees was identified as a significant predictive indicator for potential concomitant ligament insufficiency (area under curve = 0.875, P < .001) showing 80.9% of the sensitivity, 82.1% of the specificity.

Conclusions

In the surgical treatment of recalcitrant lateral epicondylitis, lateral ulnar collateral ligament reconstruction added to the débridement of extensor origin may provide better results for the patients with suspicious lateral ligament insufficiency or failed previous surgery.

Myofascial chains of the upper limb: A systematic review of anatomical studies

The presence of structural in-series continuity between skeletal muscles has been confirmed in the trunk and lower extremity. However, it is not yet clear whether the same architecture can be found in the upper limb. Therefore, the aim of the present study was to review the available literature considering the existence of myofascial chains in the shoulder-arm region. Two independent investigators performed a systematic literature search using MEDLINE (PubMed) and Google Scholar (each 1900-2019). Peer-reviewed anatomical dissection studies reporting myofascial in-series continuity in the upper extremity were included. The methodological quality of the included studies was assessed by the QUACS scale. Thirteen studies were included in the review. Analysis of these papers led to the identification of three myofascial chains: the ventral arm chain (pectoralis major, brachial fascia/biceps brachii, flexor carpi ulnaris/brachioradialis/supinator, based on five studies); the lateral arm chain (trapezius, deltoideus, lateral intermuscular septum/brachialis, brachioradialis, four studies); and the dorsal arm chain (latissiumus dorsi/teres minor/infraspinatus, triceps brachii, anconeus, extensor carpi ulnaris, six studies). There is good evidence for direct serial tissue continuity extending from the neck and shoulder region to the forearm. Despite this intriguing finding, which could have implications for health professionals and the treatment of musculoskeletal disorders, further research is needed to establish the mechanical relevance of the identified myofascial chains. Clin. Anat. 32:934-940, 2019. © 2019 Wiley Periodicals, Inc.

Role of the anconeus in the stability of a lateral ligament and common extensor origin-deficient elbow: an in vitro biomechanical study

BACKGROUND

The role of the anconeus in elbow stability has been a long-standing debate. Anatomic and electromyographic studies have suggested a potential role as a stabilizer. However, to our knowledge, no clinical or biomechanical studies have investigated its role in improving the stability of a combined lateral collateral ligament and common extensor origin (LCL + CEO)-deficient elbow.

METHODS

Seven cadaveric upper extremities were mounted in an elbow motion simulator in the varus position. An injured model was created by sectioning of the CEO and the LCL. The anconeus tendon and its aponeurosis were sutured in a Krackow fashion and tensioned to 10 N and 20 N using a transosseous tunnel. Varus-valgus angles and ulnohumeral rotations were recorded using an electromagnetic tracking system during simulated active elbow flexion with the forearm pronated and supinated.

RESULTS

During active motion, the injured model resulted in a significant increase in varus angulation (P = .0001 for pronation; P = .001 for supination) and external rotation (P = .001 for pronation; P = .003 for supination) of the ulnohumeral articulation compared with the intact state. Tensioning of the anconeus significantly decreased the varus angulation (P = .006 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) and external rotation angle (P = .008 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) of the injured elbow.

CONCLUSIONS

In the highly unstable varus elbow orientation, anconeus tensioning restores the in vitro stability of a combined LCL + CEO-deficient elbow during simulated active motion with the forearm in both pronation and supination. These results may have several clinical implications in managing symptomatic lateral elbow instability.

Radial Nerve F-wave reference values with surface electrodes from the anconeus muscle

INTRODUCTION

We sought to obtain normative values for radial nerve F-wave variables, recording with surface electrodes from the anconeus muscle.

METHODS

We tested 30 healthy participants (17 women, 13 men) and measured the following variables: number of F waves/40 traces (F%); minimum, maximum, and mean F-wave latency (FMIN, FMAX, FMED, respectively); F-wave chronodispersion (FCHR); interside differences of F% and FMIN (DF% and DFMIN, respectively).

RESULTS

The mean F% was 41.3%; the normative values of FMIN, FMED, FMAX, and FCHR were < 21.2, <22.1, <23.3, and < 4.0 ms, respectively; and normative values of DF% and DFMIN were < 16.6% and < 1.1 ms, respectively. Height was the sole independent predictor in a regression model of FMIN, FMED, and FMAX; this explained 37%-44% of the variability.

DISCUSSION

We identified a feasible and useful technique to record radial nerve F waves from the anconeus muscle and obtained normative values of F-wave variables. Muscle Nerve 59:244-246, 2019.

Pilot report: non-operative treatment of Mayo Type II olecranon fractures in any-age adult patient

BACKGROUND

We report on the non-operative treatment of Mayo Type II olecranon fractures.

METHODS

Fourteen isolated Mayo Type II olecranon fractures were treated non-operatively, followed to discharge, and retrospectively reviewed. Treatment was splinting in extension followed by protected active motion beginning 3 weeks to 4 weeks post-injury. Mayo Elbow Performance Index (MEPI) and Shortened Disabilities of the Arm, Shoulder and Hand (QuickDASH) scores were available in 86% and 64% of cases, respectively. Follow-up radiographs were obtained.

RESULTS

At discharge, the mean (SD) MEPI score was 95 (5). The mean (SD) elbow motion arc was 121° (21°). One patient re-fractured his elbow after discharge by falling on the ice. He recovered after open reduction and internal fixation. One patient (documented Marfan syndrome) developed an asymptomatic non-union. Excepting the patient who fell, no patient received additional care.

CONCLUSIONS

In this pilot report, Mayo Type II olecranon fractures were treated non-operatively to discharge. Good to excellent results were obtained in all patients according to the MEPI. Supportive care of these fractures should be comparatively studied. A downside risk to providing supportive care for these fractures was not identified.

Effect of Anconeus Muscle Blocking on Elbow Kinematics: Electromyographic, Inertial Sensors and Finite Element Study

The specific contribution of the anconeus muscle to elbow function is still uncertain. This study aimed to investigate the effect on elbow kinematics and kinetics of blocking anconeus using lidocaine. Ten healthy volunteers performed experimental trials involving flexion–extension and supination–pronation movements in horizontal and sagittal planes. Inertial sensors and surface electromyography were used to record elbow kinematics and kinetics and electrical activity from the anconeus, biceps and triceps brachii before and after blocking anconeus. Moreover, a finite element model of the elbow was created to further investigate the contribution of anconeus to elbow kinematics. The electrical activity results from the trials before blocking clearly indicated that activity of anconeus was increased during extension, suggesting that it behaves as an extensor. However, blocking anconeus had no effect on the elbow kinematics and kinetics, including the angular velocity, net torque and power of the joint. The electrical activity of the biceps and triceps brachii did not alter significantly following anconeus blocking. These results suggest that anconeus is a weak extensor, and the relative small contribution of anconeus to extension before blocking was compensated by triceps brachii. The finite element results indicated that anconeus does not contribute significantly to elbow kinematics.

Anatomical study on the innervation of the elbow capsule

OBJECTIVES

To put forward an anatomical description of the innervation of the elbow capsule, illustrated through morphological analysis on dissections.

METHODS

Thirty elbows from fresh fixed adult cadavers aged 32-74 years, of both sexes, were dissected.

RESULTS

Among the dissected arms, we observed that the median nerve did not have any branches in two arms, while it had one branch in five arms, two branches in two arms, three branches in ten arms, four branches in nine arms and five branches in two arms. The radial nerve did not have any branches in two arms, while it had one branch in two arms, two branches in nine arms, three branches in ten arms, four branches in five arms and five branches in two arms. The ulnar nerve did not have any branches in three arms, while it had one branch in six arms, two branches in four arms, three branches in five arms, four branches in seven arms, five branches in four arms and six branches in one arm.

CONCLUSIONS

We observed branches of the radial, ulnar and medial nerves in the elbow joint, and a close relationship between their capsular and motor branches.

In vivo measurement of fascicle length and pennation of the human anconeus muscle at several elbow joint angles

Ultrasound imaging has facilitated the reliable measure of the architectural variables fascicle length (LF ) and pennation angle (PA), at rest and during static and dynamic contractions in many human skeletal muscles in vivo. Despite its small size and very modest contribution to elbow extension torque, the anconeus muscle has proven a useful model for the study of neuromuscular function in health and disease. Recent single motor unit (MU) studies in the anconeus have reported discrete and identifiable individual trains of MU potentials from intramuscular electromyography (EMG) recordings during dynamic elbow extensions. It is unknown whether the anconeus has unique architectural features related to alterations in LF and PA throughout the elbow joint range of motion that may help explain these high-quality recordings. Previous anatomical studies have investigated this muscle in cadavers and at mainly one elbow joint angle. The purpose of this study was to measure in vivo PA and LF of the anconeus muscle in a relaxed state at different degrees of elbow flexion using ultrasonography. Ultrasound images were collected from 10 healthy males (25 ± 3 years) at 135°, 120°, 90°, 45°, and 0° of elbow flexion. Average values of LF decreased by 6 mm (10%), 6 mm (12%), and 4 mm (9%) from 135-120°, 120-90°, and 90-45° of elbow flexion, respectively, whereas average PA values increased by 1° (9%), 1° (8%), and 2° (14%) from 135-120°, 120-90°, and 45-0°, respectively. The results indicate that anconeus muscle architecture is dynamic, undergoing moderate changes with elbow joint excursion that are similar to other limb muscles reported elsewhere. The data obtained here are more comprehensive and representative of architectural changes at various elbow joint positions than those data reported in cadaveric studies. Furthermore, the results of this study indicate that despite experiencing similar relative changes in muscle architecture to other skeletal muscles about the elbow joint, the minimal absolute changes in LF of the anconeus likely contribute to the clarity of intramuscular EMG previously reported in this muscle.

Anconeus pedicle olecranon flip osteotomy: an approach for the fixation of complex intra-articular distal humeral fractures

In order to achieve satisfactory reduction of complex distal humeral fractures, adequate exposure of the fracture fragments and the joint surface is required. Several surgical exposures have been described for distal humeral fractures. We report our experience using the anconeus pedicle olecranon flip osteotomy approach. This involves detachment of the triceps along with a sliver of olecranon, which retains the anconeus pedicle. We report the use of this approach in ten patients (six male, four female) with a mean age of 38.4 years (28 to 51). The mean follow-up was 15 months (12 to 18) with no loss to follow-up. Elbow function was graded using the Mayo Score. The results were excellent in four patients, good in five and fair in one patient. The mean time to both fracture and osteotomy union was 10.6 weeks (8 to 12) and 7.1 weeks (6 to 8), respectively. We found this approach gave reliably good exposure for these difficult fractures enabling anatomical reduction and bicondylar plating without complications.

Hypotheses for ongoing evolution of muscles of the upper extremity

There are organs and muscles in the human body that may be considered rudimentary in that they have insignificant or undetermined function. Several such muscles are found in the upper extremity. In this review, four muscles that appear to be undergoing evolutionary changes are discussed: flexor digitorum superficialis to the fifth finger, anconeus, palmaris longus, and anconeus epitrochlearis. The present study synthesizes, advances and extends previously described work about these muscles and extends the hypotheses and concludes that: (a) the flexor digitorum superficialis to the fifth finger is currently under adaptive evolution, (b) the anconeus has currently stabilized its evolution and is serving as a transient stability augmenter during a short portion of the human lifespan, and (c) the entire distal upper extremity is currently in the process of undergoing evolutionary change. Understanding of these muscles and their evolutionary context is important for understanding of impact on function, dysfunction, treatment and future research.

Functional differences between anatomical regions of the anconeus muscle in humans

This study sought to resolve a longstanding debate of the function of anconeus. Intramuscular and surface electromyography electrodes recorded muscle activity from two regions of anconeus and from typical elbow flexion and extension muscles. Eleven participants performed pronation-supination around the medial and lateral axes of the forearm, elbow flexion-extension in pronation, supination and neutral positions of the forearm, and gripping. Maximal voluntary contractions (MVC) and submaximal (10% MVC) force-matching tasks were completed. Activity varied between longitudinal (AL) and transverse (AT) segments of anconeus. Although both muscle regions were active across multiple directions (including opposing directions), AL was more active during pronation than supination, whereas AT showed no such difference. During pronation, activity of AL and AT was greatest about the lateral forearm axis. AT was more active during elbow extension with the forearm in pronation, whereas AL did not differ between pronated and neutral forearm alignment. These findings are consistent with the proposal that AL makes a contribution to control of abduction of the ulna during forearm pronation. Different effects of forearm position on AL and AT activity during elbow extension may be explained by the anatomical differences between the regions. These data suggest anconeus performs multiple functions at the elbow and forearm and this varies between anatomically distinct regions of the muscle.

Soft tissue constraint injuries in complex elbow instability: prevalence, pathoanatomy, and classification

The types and prevalence of soft tissue constraint injuries associated with complex elbow instability have been rarely investigated. The purpose of this study was to analyze the intraoperative findings of soft tissue constraint injuries in complex elbow instability and provide a comprehensive classification of these lesions. Forty-seven patients undergoing surgery for complex elbow instability were prospectively analyzed. Ligament injuries were classified as simple or complex lesions, depending on whether the ligament was damaged at a single zone or 2 to 3 zones, including its proximal, middle, and distal portions. Posterolateral capsule injuries were classified as small or large in the presence of capsular avulsions smaller than or larger than 1 cm, respectively. The presence of lesions of the common extensor and flexor-pronator muscles were also recorded. Ligament injuries were found in 96% of patients. The lateral collateral ligament showed a simple lesion, including a proximal and distal avulsion, in 19% and 2% of patients, respectively, and a middle-zone tear in 13%. Complex lesions, including the association of a middle-zone tear with a proximal or distal avulsion, were found in 47% and 6% of patients, respectively, and a combination of proximal, distal, and middle-zone injuries in 4%. Small and large posterolateral capsule lesions were found in 49% and 17% of patients, respectively. A medial collateral ligament injury was present in 45% of patients. A high prevalence of soft tissue constraint lesions was found to be associated with complex elbow instability. Soft tissue constraint status should be carefully evaluated pre- and intraoperatively in patients with complex elbow instability. The classification reported herein may be helpful in planning the proper treatment of these complex injuries.