Digital smart internal fixation surgery for coronal process basal fracture with normal joint spaces or radius-shortening: Occult factor of radius-ulna load sharing

BACKGROUND

Reasonable postoperative humeroradial and humeroulnar joint spaces maybe an important indicator in biomechanical stability of smart internal fixation surgery for coronoid process basal fractures (CPBF). The aim of this study is to compare elbow articular stresses and elbow-forearm stability under smart internal fixations for the CPBF between normal elbow joint spaces and radius-shortening, and to determine the occult factor of radius-ulna load sharing.

METHODS

CT images of 70 volunteers with intact elbow joints were retrospectively collected for accurate three-dimensional reconstruction to measure the longitudinal and transverse joint spaces. Two groups of ten finite element (FE) models were established prospectively between normal joint space and radius-shortening with 2.0 mm, including intact elbow joint and forearm, elbow-forearm with CPBF trauma, anterior or posterior double screws-cancellous bone fixation, mini-plate-cancellous bone fixation. Three sets of physiological loads (compression, valgus, varus) were used for FE intelligent calculation, FE model verification, and biomechanical and motion analysis.

RESULTS

The stress distribution between coronoid process and radial head, compression displacements and valgus angles of elbow-forearm in the three smart fixation models of the normal joint spaces were close to those of corresponding intact elbow model, but were significantly different from those of preoperative CPBF models and fixed radius-shortening models. The maximum stresses of three smart fixation instrument models of normal joint spaces were significantly smaller than those of the corresponding fixed radius-shortening models.

CONCLUSIONS

On the basis of the existing trauma of the elbow-forearm system in clinical practice, which is a dominant factor affecting radius-ulna load sharing, the elbow joint longitudinal space has been found to be the occult factor affecting radius-ulna load sharing. The stability and load sharing of radius and ulna after three kinds of smart fixations of the CPBF is not only related to the anatomical and biomechanical stability principles of smart internal fixations, but also closely related to postoperative elbow joint longitudinal space.

Comprehensive analysis and classification of retrocondylar ulnar groove morphology using CT imaging in an average population of adults

PURPOSE

Anatomical variations of the concave shaped retrocondylar ulnar groove (RUG) can contribute to ulnar nerve instability. However, there are currently limited available standardized data describing the anatomy of the RUG based on radiologic imaging, such as computed tomography (CT). This study aims to provide a comprehensive description and classification of RUG anatomy based on RUG angle measurements.

METHODS

400 CT scans of the elbows of adults showing no signs of osseous damage were evaluated. RUG angles were measured in four anatomically defined axial planes that spanned from the proximal to the distal end of the RUG. Furthermore, distance measurements at the medial epicondyle were conducted. A classification system for the RUG is proposed based on the acquired RUG angles, aiming to categorize the individual angles according to the 25th and 75th percentiles.

RESULTS

RUG angles were significantly larger in males compared to females (p < 0.001) accompanied by larger distances including the off-set and height of the medial epicondyle (p < 0.001). RUG angles decreased from proximal to distal locations (p < 0.05).

CONCLUSION

This study revealed that men exhibited larger RUG angles compared to women, indicating a less-concave shape of the RUG in men. Introducing an objective RUG classification system can improve our understanding of anatomical variations and potentially find application in diagnostics and preoperative planning.

Morphology of Proximal Ulna Bare Area: A Guide for Olecranon Osteotomy

PURPOSE

Olecranon osteotomy is commonly used to obtain access to the distal humerus for fracture fixation. The goal of this study was to accurately describe the anatomy of the bare area to minimize articular cartilage damage while performing olecranon osteotomies.

METHODS

Twenty cadaveric ulnae were denuded to expose the bare area. Laser surface mapping was used to create 3-dimensional models, and the nonarticular portions of the ulnae were digitally measured.

RESULTS

The morphology of the bare area from all aspects of the proximal ulna was defined. The central bare area was consistent in its location, 4.9 ± 1.5 mm distal to the deepest portion of the trochlear notch and 23.2 ± 2.3 mm distal to the olecranon tip. The maximum chevron osteotomy apical angle to stay within the bare area averaged 110° ± 11.8°. However, there was little tolerance for error without the risk of violating the articular cartilage. With transverse osteotomy, averaging 18° ± 10.6° in the coronal plane, there is less risk of damaging the articular cartilage.

CONCLUSIONS

Transverse osteotomy perpendicular to the posterior surface of the ulna aiming at the visible bare area on the medial and lateral sides of the greater sigmoid notch may reduce the chances of violating the nonvisible articular cartilage of the proximal ulna. Based on the findings of this study, if chevron osteotomy is used, a shallow apex distal angle of more than 110° is recommended.

CLINICAL RELEVANCE

This study provides intraoperative landmarks to guide surgeons performing olecranon osteotomies to stay within the bare area.

Does the articularis cubiti muscle really exist? Anatomical, histological, and magnetic resonance imaging study with a narrative review of literature

Although the term articularis cubiti muscle is incorporated in the official anatomical nomenclature, only sparse data about its appearance are available. It is usually described as few fibres originating from the medial head of the triceps brachii muscle and inserting to the capsule of the elbow joint. However, the most recent observations regarding the morphological relations in the posterior elbow region point towards the absence of a well-defined muscle. Therefore, this study was designed to verify the existence of the articularis cubiti muscle in question and to compile more data on the topographical features of the subtricipital area near the posterior aspect of the elbow. To address these questions, 20 embalmed upper limbs were dissected, and seven samples were collected for histological analysis. The laboratory findings were then correlated with 20 magnetic resonance imaging (MRI) scans of the elbow. Consequently, a narrative review of literature was performed to gain more information on the discussed muscle in a historical context. Upon the anatomical dissection, muscular fibres running from the posterior aspect of the shaft of the humerus to the elbow joint capsule and olecranon were identified in 100% of cases. Histologically, the connection with the joint capsule was provided via winding bands of connective tissue. On MRIs, the muscular fibres resembled a well-demarcated thin muscle located underneath the medial head of the triceps brachii muscle. Combined with the review of literature, we concluded that the constant articularis cubiti muscle originates from the posterior shaft of the humerus and attaches indirectly to the posterior aspect of the elbow joint capsule and directly to the superior portion of the olecranon. The obtained results slightly differ from the modern description, but are in agreement with the original publication, which has become misinterpreted throughout time. Presumably, the misused description has led to questioning the existence of an independent muscle. Moreover, our findings attribute to the articularis cubiti muscle, a function in pulling on the posterior aspect of the elbow joint capsule to prevent its entrapment, and possibly also a minor role in extension of the forearm. The presented results should be taken into consideration when intervening with the posterior aspect of the elbow joint because the articularis cubiti muscle poses a consistently appearing landmark.

Morphometrics of the coronoid process and the radial notch of the ulna: implications for fracture assessment

PURPOSE

A comprehensive analysis of the morphology of fractures of the coronoid process (CP) can aid diagnosis and guide treatment. The involvement of the radial notch of the ulna (RN)-e.g., in anterolateral facet fractures and transverse fractures of the CP-may influence the biomechanical conditions of the proximal radioulnar joint. However, the morphometric relation between the CP and the RN and the extent to what the proximal radioulnar joint can be affected in these types of fractures is unknown.

METHODS

A total of 113 embalmed, cadaveric ulnae were dissected. All soft tissue was removed. Strictly lateral, high-resolution photographs were taken and digitally analyzed. The height of the CP and its relation to the RN was measured. Sex differences and correlations between measured parameters were calculated.

RESULTS

Mean height of the CP was 16 mm (range: 12-23 mm; SD: 2). Mean height of the RN was 16 mm (11-25 mm; 2.2). The 50% mark of the CP corresponded to 18% (0-56%; 11.2) of the height of the RN. No significant differences were found between male and female specimens.

CONCLUSION

The RN of the ulna extends only to a small part to the CP. Transverse or anterolateral fractures of less than 50% of the coronoid process may involve only a small portion of the proximal radioulnar joint.

Morphological characteristics of coronoid process and revisiting definition of coronoid hyperplasia

The aim of this study was to assess the morphological characteristics of the coronoid process (CP) and define coronoid hyperplasia (CH) using cadaveric mandibles of a Caucasian population. A sample of 151 adult dry cadaveric mandibles (302 CPs) was acquired. Three distances were measured, which included the width, height, and length of CP. The surface area measurements involved area A: above the width distance line; area B: between incisura mandibulae-Alveolar ridge line and width distance line; area C: between distance lines of width and height. Finally, angulations of the CP and gonial angles were identified. Both length and surface area A + B acted as hyperplastic indicators. Based on the selection criteria, a sample of 197 CPs was included. The hooked shape (59%) was most commonly observed. No significant difference existed between left and right sides (p > 0.05). The mean values of length and surface area A + B were 2.2 ± 0.3 cm and 3.3 ± 0.8 cm2, and any values above 2.7 cm (n = 5 CPs- 2.5%) and 5.0 cm2 (n = 9 CPs- 4.6%) were described as hyperplastic, respectively. The presented data could act as quantitative reference for differentiating between normal and hyperplastic conditions.

The lateral ulnar collateral ligament: Anatomical and structural study for clinical application in the diagnosis and treatment of elbow lateral ligament injuries

The lateral ulnar collateral ligament (LUCL) is considered one of the main stabilizers of the elbow. However, its anatomical description is not well established. Imaging techniques do not always have agreed upon parameters for the study of this ligament. Therefore, herein, we studied the macro and microanatomy of the LUCL to establish its morphological and morphometric characteristics more precisely. Fifty-five fresh-frozen human elbows underwent dissection of the lateral collateral ligament. Morphological characteristics were studied in detail. Ultrasound (US) and magnetic resonance (MR) were done before dissection. Two specimens were selected for PGP 9.5 S immunohistochemistry. Ten additional elbows were analyzed by E12 sheet plastination. LUCL was identified in all specimens and clearly defined by E12 semi-thin sections. It fused with the common extensor tendon and the radial ligament. The total length of the LUCL was 48.50 mm at 90°, 46.76 mm at maximum flexion and 44.10 mm at complete extension. Three morphological insertion variants were identified. Both US and MR identified the LUCL in all cases. It was hypoechoic in the middle and distal third in 85%. The LUCL was hypointense on MR in 95%. Free nerve endings were present on histology. The LUCL is closely related to the anular ligament. It is stretched during flexion and supination. US and MR can reliably identify its fibers. Anatomical data are relevant to the surgeon who repairs the ligaments of the elbow. Also, to the radiologist and pain physician who interpret imaging and treat patients with pain syndromes of the elbow.

Morphometric feature description of the proximal ulna based on quantitative measurement: a key consideration for implant design

PURPOSE

To perform quantitative measurements of the anatomic morphology of the proximal ulna and establish the morphologic references based on Chinese for the surgical protocol and implant design.

METHODS

The computed tomography data of 156 upper extremities were involved in this study. The ulna model was reconstructed in Mimics. Ten distance and 6 angle parameters were measured by 4 independent investigators with a new quantitative measurement method. The intraclass correlation coefficient was used to evaluate the measuring reliability. Gender and side differences of measured parameters were evaluated.

RESULTS

Measurements showed a mean coronoid height of 15 mm, which was 42% of ulnar height with gender-specific differences (mean 16 mm in men and 14 mm in women, P < 0.001). A mean unsupported anteromedial facet width of 8 mm was 61% of the coronoid anteromedial facet. A larger opening angle correlates to a larger olecranon-diaphysis angle (P < 0.001) and larger coronoid height (P = 0.001). A mean proximal ulna dorsal angulation of 4.7° is present in 80% of models at an average of 52 mm distal to olecranon tip. The average proximal ulna varus angulation was 16° at a mean of 74 mm distal to the olecranon tip. Morphological features between the left and right sides were highly consistent. The ICC was between 0.789 and 0.978 for inter-observer and between 0.696 and 0.997 for intra-observer reliability.

CONCLUSIONS

The proximal ulna features variable morphology but minor side differences among individuals. Over half of the anteromedial facet was not supported by the proximal ulnar diaphysis, making the coronoid vulnerable to elbow trauma. Preconditioning or customized design of the ulnar plate in the clinical setting with the help of contralateral morphology may be a good choice.

Anatomic evaluation of the triceps tendon insertion at the proximal olecranon regarding placement of fracture fixation devices

PURPOSE

Olecranon fractures, especially with a small proximal fragment, remain a surgical challenge. Soft tissue irritation and affection of the triceps muscle bear a risk of complications. In order to find an area for a soft-tissue sparing placement of implants in the treatment of olecranon fractures, we aimed to define and measure the segments of the proximal olecranon and evaluate them regarding possible plate placement.

METHODS

We investigated 82 elbow joints. Ethical approval was obtained from the local ethics committee, After positioning in an arm holder and a posterior approach we described the morphology of the triceps footprint, evaluated and measured the surface area of the triceps and posterior capsule and correlated the results to easily measurable anatomical landmarks.

RESULTS

We found a bipartite insertional footprint with a superficial tendinous triceps insertion of 218.2 mm² (± 41.2, range 124.7-343.2), a capsular insertion of 159.3 mm² (± 30.2, range 99.0-232.1) and a deep, muscular triceps insertion area of 138.1 mm² (± 30.2, range 79.9-227.5). Olecranon height was 26.7 mm (± 2.3, range 20.5-32.2), and olecranon width was 25.3 mm (± 2.4, range 20.9-30.4). Average correlation between the size of the deep insertion and ulnar (r = 0.314) and radial length (r = 0.298) was obtained.

CONCLUSIONS

We demonstrated the bipartite morphology of the distal triceps footprint and that the deep muscular triceps insertion area by its measured size could be a possible site for the placement of fracture fixations devices. The size correlates with ulnar and radial length.

Just noticeable differences for elbow joint torque feedback

Joint torque feedback is a new and promising means of kinesthetic feedback imposed by a wearable device. The torque feedback provides the wearer temporal and spatial information during a motion task. Nevertheless, little research has been conducted on quantifying the psychophysical parameters of how well humans can perceive external torques under various joint conditions. This study aims to investigate the just noticeable difference (JND) perceptual ability of the elbow joint to joint torques. The paper focuses on the ability of two primary joint proprioceptors, the Golgi-tendon organ (GTO) and muscle spindle (MS), to detect elbow torques, since touch and pressure sensors were masked. We studied 14 subjects while the arm was isometrically contracted (static condition) and was moving at a constant speed (dynamic condition). In total there were 10 joint conditions investigated, which varied the direction of the arm's movement and the preload direction as well as torque direction. The JND torques under static conditions ranged from 0.097 Nm with no preload to 0.197 Nm with a preload of 1.28 Nm. The maximum dynamic JND torques were 0.799 Nm and 0.428 Nm, when the arm was flexing and extending at 213 degrees per second, respectively.

Relationship between morphology of transverse bundle of ulnar collateral ligament and adjacent tissues

PURPOSE

The purpose of this study was to clarify the incidence of the transverse bundle (TB) of the ulnar collateral ligament (UCL), the relationships between TB morphology and morphology of the anterior bundle (AB) or posterior bundle (PB) of the UCL, and the relationship between the TB and the posterior common tendon (PCT).

METHODS

This study examined 38 elbows from 23 cadavers. TB, AB, and PB were classified morphologically. The TB was classified as: type I, TB does not continue the entire length of the AB; or type II, TB continues the entire length of the AB. The AB and PB were classified as: type I, could be separated as single bundles; or type II, could not be separated. We also observed specimens by focusing on the continuity between the TB and PCT. Fisher's exact test was used to examine the relationship between TB type and AB or PB type.

RESULTS

A TB was identified in all 38 elbows (100%), and continued to the AB in all specimens. No significant relationship was evident between TB type and AB or PB type. Continuity of TB fibers and the PCT was seen in 26 elbows (72%).

CONCLUSION

This study suggested that the morphology of the transverse bundle may be unrelated to the morphology of the anterior bundle or posterior bundle.

Elbow Fractures

The elbow joint consists of the humeroulnar, humeroradial, and proximal radioulnar joints. Elbow stability is maintained by a combination of static and dynamic constraints. Elbow fractures are challenging to treat because the articular surfaces must be restored perfectly and associated soft tissue injuries must be recognized and appropriately managed. Most elbow fractures are best treated operatively with restoration of normal bony anatomy and rigid internal fixation and repair and/or reconstruction of the collateral ligaments. Advanced imaging, improved understanding of the complex anatomy of the elbow joint, and improved fixation techniques have contributed to improved elbow fracture outcomes.

Bone Mineral Density and Microstructure of the Elbow in Baseball Pitchers: An Analysis by Second-Generation HR-pQCT

BACKGROUND

Baseball pitchers' elbows are exposed to repeated overloading during the throwing motion, which causes bone structural changes such as bone sclerosis and osteophyte formation. They have been observed by clinical CT and MRI, while the bone microstructural change has not yet been studied in vivo. The aims of this study were to establish a method of imaging the elbow joint using second-generation high-resolution peripheral quantitative CT and to investigate the bone microstructural change in baseball pitchers' dominant elbows.

METHODS

The subjects were 17 baseball pitchers. The elbow was fixed using a custom-made cast and scanned by second-generation high-resolution peripheral quantitative CT. The scan conditions were as follows: voxel size 60.7 μm, integration time 43 ms, scan length 30.6 mm, and total scan time 8 min. Volumetric bone mineral density (vBMD) and trabecular bone microstructure were analyzed in the 6.5-mm³ cubic regions set in the capitellum and trochlea, and the dominant and nondominant elbows were compared.

RESULTS

vBMD, bone volume fraction (BV/TV), and trabecular thickness (Tb.Th) at the capitellum were significantly higher in the dominant elbow than in the nondominant elbow. On the other hand, no parameters at the trochlea were significantly different.

CONCLUSIONS

Higher vBMD accompanied by thicker trabecular bone was observed at the capitellum. These bone microstructural changes would reflect the valgus stress generated by the pitching motion in the elbow joint.

The investigation of the carrying angle of the elbow in fetal period

PURPOSE

The aim of our study was to determine the carrying angle in human fetuses and to identify variations in carrying angle by gender, fetal age and elbow side in fetal period.

METHODS

This study was carried out on 20 dead human fetuses (13 males, 7 females) fixed with formaldehyde, aged between 10-35 weeks of gestation, without external anomalies. Ages of the fetuses were determined according to the general growth parameters. First, the fetus arms were positioned in 180° extension and the forearms were placed in supination. Then the midpoints of the caput humeri, the elbow joint and the wrist were determined. The photographs were taken from the anterior aspect. The distances between the reference points and carrying angles were measured using ImageJ program in the photographs.

RESULTS

The mean ± SD values of carrying angle were 14.18 ± 5.52 and 8.21 ± 4.82 degrees in males and in females, respectively. Although there was no difference between right and left sides within both genders, there was a significant difference between genders (p < 0.05). Gestational age and fetal carrying angle showed a medium negative correlation at the right arm and a weak negative correlation at the left arm.

CONCLUSION

The existence of a significant difference between fetal carrying angles belong to different genders suggested that the sexual dimorphism of carrying angles may be starting at the early intrauterine period. The carrying angle should be explained with the studies performed in larger series in the prenatal and postnatal periods.

Functional and Surgical Anatomy of the Upper Limb: What the Radiologist Needs to Know

The anatomy of the upper limb is complex and allows for exceptional functionality. The movements of the joints of the shoulder, elbow, and wrist represent a complex dynamic interaction of muscles, ligaments, and bony articulations. A solid understanding and of the characteristics and reciprocal actions of the anatomic elements of the joints of the upper limb helps explain the mechanisms and patterns of injury. This article focuses on the anatomy and functionality of the shoulder, elbow, and wrist, with emphasis on the stabilizing mechanisms, to set the foundation for understanding the occurrence of pathologic conditions.

Intra-Observer and Inter-Observer Reliability of Shaft Condylar Angle and Lateral Capitellohumeral Angle: Evaluation Based on Reliability in Different Ages and Levels of Experience

OBJECTIVES

The aims of this paper were: (i) to examine the intra-observer and inter-observer reliability of the shaft-condylar angle (SCA) and the lateral capitellohumeral angle (LCHA); (ii) to study the influence of experience level on the inter-observer and intra-observer reliability; and (iii) to determine the influence of the the age of the patients on reliability.

METHOD

A retrospective cohort study was conducted. The study reviewed 81 elbow radiographs. The patients were aged between 2 and 13 years. All the images taken between 2000 and 2017 were independently measured by a senior pediatric orthopaedic surgeon, a pediatric orthopaedic surgeon, a pediatric orthopaedic fellow, an orthopaedic chief resident, a general practitioner, and a pediatric orthopaedic research assistant. Measurement was performed two times within a 2-week interval. Inexperienced observers (general practitioner and research assistant) were supervised by senior pediatric orthopaedic surgeons for at least 30 radiographs before performing the measurement. Inclusion criteria were as follows: (i) age 2-13 years; and (ii) no previous elbow fracture.

EXCLUSION CRITERIA

elbow radiographs do not show true lateral view. The intraclass correlation coefficient (ICC) was used to calculate the reliability.

RESULTS

The mean values of SCA and LCHA were 43° and 48°, respectively. For SCA, intra-observer reliability was excellent (ICC = 0.85) for one observer, good (range = 0.73-0.76) for three observers, and moderate (0.59) for one observer. Inter-observer reliability was moderate (0.48, 0.58), whereas the reliability categorized by age group showed excellent agreement (0.88-0.94). For LCHA, intra-observer reliability was excellent (0.84-0.89) for three observers and good (0.66-0.80) for two observers. Inter-observer reliability was moderate (0.44-0.45). Conversely, the reliability classified by age group showed excellent agreement (0.83-0.91).

CONCLUSION

Intra-observer reliability for LCHA and SCA were excellent to good for most observers. Inter-observer reliability was moderate for LCHA and SCA. Reliability classified by age group showed excellent to good agreement. Reliability was influenced by the level of experience, especially for non-medical staff.

Transbrachioradialis Approach to the Radial Tunnel: An Anatomic Study of 5 Potential Compression Sites

BACKGROUND

Recent anatomic studies have failed to demonstrate a single utilitarian approach to intraoperative identification and surgical release of all 5 potential sites of posterior interosseous nerve (PIN) compression in the radial tunnel. This study examines if a single incision brachioradialis-splitting approach without the use of additional anatomic windows is capable of adequately exposing the entire length of the radial tunnel, including all 5 sites of PIN compression to allow for adequate release.

METHODS

Ten fresh frozen cadaver forearms (6 female, 4 male) were dissected utilizing a curvilinear 7 cm incision over the brachioradialis. The muscle belly was split via simple blunt retraction, exposing the radial tunnel. The PIN was identified and mobilized at 5 compression sites: radiocapitellar joint (RCJ), radial recurrent vessels (Leash of Henry), fibrous medioproximal edge of extensor carpe radialis brevis, arcade of Frohse, and distal edge of supinator.

RESULTS

The PIN was identified and effectively released in all specimens without difficulty from this single approach. All 5 sites of compression were visible and accessible through the brachioradialis-split approach. Specifically, there was no difficulty in identifying and releasing the PIN at the distal edge of supinator.

CONCLUSIONS

Radial tunnel syndrome is defined as PIN compression within the radial tunnel spanning from the fibrous RCJ to the distal edge of the supinator. A single brachioradialis-splitting approach is adequate for complete visualization and release of all compression sites of the radial tunnel. Utilizing this technique allows for surgical access and ease as well as minimizing necessity for additional windows or multiple incisions.

Elbow Joint Angle Estimation with Surface Electromyography Using Autoregressive Models

This paper presents a method to estimate the elbow joint angle from surface electromyography (sEMG) measurements of biceps, triceps and brachioradialis. This estimation is of major importance for the design of human robot interfaces based on sEMG. It is also relevant to model the muscular system and to design biomimetic mechanisms. However, the processing and interpretation of electromyographic signals is challenging due to nonlinearities, unmodeled muscle dynamics, noise and interferences. In order to determine an estimation model and a calibration procedure for the model parameters, a set of experiments were carried out with six subjects. The experiments consisted of series of continuous (cyclical) and discrete elbow flexo-extensions with three different loads (i.e. 0 kg, 1.5kg and 3 kg). The sEMG data from the biceps brachii, triceps brachii and brachioradialis and the joint angle were recorded. Four different modeling techniques were evaluated: State Space (SS), Autoregressive with Exogenous Input (ARX), Autoregressive Moving-Average with Exogenous Input (ARMAX), Autoregressive Integrated Moving-Average with Exogenous Input (ARIMAX). After the model was selected, a second experiment was performed in order to validate the estimation procedure. The results show a procedure to estimate the EMG-to-angle relation with high correlation and low meansquare- root errors with respect to the measured angle data.

Radial Head Fracture Fixation Using Tripod Technique With Headless Compression Screws

Radial head and neck fractures are one of the most common elbow fractures, comprising 2% to 5% of all fractures, and 30% of elbow fractures. Although uncomplicated Mason type I fractures can be managed nonsurgically, Mason type II-IV fractures require additional intervention. Mason type II-III fractures with 3 or fewer fragments are typically treated with open reduction and internal fixation using 2 to 3 lag screws. Transverse radial neck involvement or axial instability with screw-only fixation has historically required the additional use of a mini fragment T-plate or locking proximal radius plate. More recently, less invasive techniques such as the cross-screw and tripod techniques have been proposed. The purpose of this paper is to detail and demonstrate the proper implementation of the tripod technique using headless compression screws.

The annular ligament-revisited

BACKGROUND

Studies investigating the annular ligament have presented confusing information about its anatomy and nomenclature. Cadaver elbow dissections were used to clarify the anatomy and terminology of the annular ligament.

METHODS

Nineteen elbows were dissected (7 fresh frozen and 12 embalmed). Target structures were identified, photographed, and measured by independent observers.

RESULTS

There are 3 layers to the lateral elbow ligaments: the superficial lateral ulnar collateral and radial collateral ligament; a deeper layer of the superior oblique band (SOB) and inferior oblique band (IOB) of the annular ligament; and the deepest capsular layer. The annular ligament measured 9.5 ± 1.4 mm anteriorly. The SOB (15/19) was 3.9 ± 1.0 mm wide by 10.5 ± 3.8 mm long. The IOB (13/19) was 3.6 ± 1.1 mm wide by 11.4 ± 4.2 mm long. The IOB inserts onto the anterior proximal ulna rather than the supinator crest. The anterior oblique band (8/19) was 3.8 ± 1.7 mm wide.

CONCLUSION

The SOB and IOB were present in the majority of specimens. The previously described accessory lateral collateral ligament is a localized thickening on the lateral ligament complex arising from the supinator insertion independent of the IOB that attaches to the annular ligament inferiorly and distally and attaches onto the proximal anterior ulna at the bicipital fossa floor, medial to the supinator crest.

Sonography of the Pronator Teres: Normal and Pathologic Appearances

The pronator teres muscle is rarely examined during a routine sonographic examination of the elbow joint. Nevertheless, it can be affected by a variety of conditions, including trauma and tumors, and can be implicated in compression of the median nerve. This pictorial essay first illustrates the anatomy and biomechanics of the pronator teres. Then we present the sonographic technique for examination, normal sonographic appearance, and anatomic variations of the pronator teres and adjacent structures as well as sonography of their main disorders. Normal and pathologic sonographic appearances are correlated with magnetic resonance imaging and radiographic results.

Modified Anterolateral Portals in Elbow Arthroscopy: A Cadaveric Study on Safety

PURPOSE

To evaluate the proximity to the radial nerve on cadaveric specimens of 2 modified anterolateral portals used for elbow arthroscopy.

METHODS

Ten fresh cadaveric elbow specimens were prepared. Four-millimeter Steinman pins were inserted into 3 anterolateral portal sites in relation to the lateral epicondyle: (1) the standard distal anterolateral portal, (2) a modified direct anterolateral portal, and (3) a modified proximal anterolateral portal. These were defined as follows: direct portals 2 cm directly anterior to the lateral epicondyle, and proximal portals 2 cm proximal and 2 cm directly anterior to the lateral epicondyle. Each elbow was then dissected to reveal the course of the radial nerve. Digital photographs were taken of each specimen, and the distance from the Steinman pin to the radial nerve was measured.

RESULTS

The modified proximal anterolateral and direct anterolateral portals were found to be a statistically significant distance from the radial nerve compare to the distal portal site (P = .011 and P = .0011, respectively). No significant difference was found in the proximity of the radial nerve between the modified proximal and direct anterolateral portals (P = .25). Inadequate imaging was found at a single portal site for the proximal site; 9 specimens were used for analysis of this portal with 10 complete specimens for the other 2 sites.

CONCLUSIONS

In cadaveric analysis, both the modified proximal and direct lateral portals provide adequate distance from the radial nerve and may be safe for clinical use. In this study, the distal anterolateral portal was in close proximity of the radial nerve and may result in iatrogenic injury in the clinical setting.

CLINICAL RELEVANCE

This is a cadaveric analysis of 2 modified portal locations at the anterolateral elbow for use in elbow arthroscopy. Further clinical studies are needed prior to determining their absolute safety in comparison to previously identified portal sites.

[Preliminary application of three dimensional printing personalized navigation template in assisting total elbow replacement for patients with elbow tumor]

Objective

To explore the clinical methods of resection of elbow tumor and total elbow replacement with custom personalized prosthesis based on three dimensional (3-D) printing navigation template.

Methods

In August 2016, a 63-year-old male patient with left elbow joint tumor was treated, with the discovery of the left distal humerus huge mass over 3 months, with elbow pain, activity limitation of admission. Computer-assisted reduction technique combined with 3-D printing was used to simulate preoperative tumor resection, a customized personal prosthesis was developed; tumor was accurately excised during operation, and the clinical result was evaluated after operation.

Results

The time was 46 minutes for tumor resection, and was 95 minutes for personalized implant and allograft bone without fluoroscopy. X-ray and CT examination at 1 week after operation showed good position of artificial elbow joint; the anteversion of ulna prosthesis was 30° and the elbow carrying angle was 15°, which were consistent with the simulated results before surgery. The finger flexion was normal at 1 month after operation; the range of motion was 0-130° for elbow flexion and extension, 80° for forearm pronation, and 80° for forearm supination. The elbow function was able to meet the needs of daily life at 7 months after operation, and no recurrence and metastasis of tumor were observed.

Conclusion

For limb salvage of elbow joint, computer aided design can make preoperative surgical simulation; the navigation template can improve surgical precision; and the function of elbow joint can be reconstructed with customized and personlized prosthesis for total elbow replacement.

Anatomical variations of the trochlear notch angle: MRI analysis of 78 elbows

BACKGROUND

Little is known about the anatomical variations of the trochlear notch angle, nor do we know whether the cartilaginous layer modifies the trochlear bony contour. Our aim was to assess the variability of the bony and cartilaginous trochlear notch angles.

MATERIALS AND METHODS

We assessed 78 healthy elbows (39 patients, 19 females and 20 males) with a mean age of 28 years (range 21-32). High-definition MRI coronal scans at the level of the flexion-extension axis were performed. The cartilage thickness, the notch angle, and trochlear width were calculated at the level of the deepest point of the trochlear sulcus, the edge of the lateral and medial ridge. Patient height was used as indirect measurement of humerus length. Pearson correlation and Student's t tests were performed.

RESULTS

Mean cartilage thickness was 1.00 mm (range 0.62-1.83), with significant differences between the medial trochlear ridge and the other landmarks. The notch angle ranged from 124° to 156° (mean 142°) with no differences between the bony and cartilage layers. Trochlear width ranged from 1.57 to 2.75 cm (mean 2.24) and correlated with humerus length. No correlation emerged between the trochlear notch angle, trochlear width, or humerus length. The only significant difference between sexes was the width value, with a wider trochlea in males.

CONCLUSIONS

The trochlear notch angle varies considerably, determining anatomical variations in trochlear shape which ranges from less concave to more concave types. Moreover, the cartilaginous layer does not modify this angle at the level examined. These findings may be relevant to anatomical implant design for distal humerus hemiarthroplasty.

[The bare area of the proximal ulna : An anatomical study on optimizing olecranon osteotomy]

BACKGROUND

Olecranon osteotomy is an established approach for the treatment of distal humerus fractures. It should be performed through the bare area of the proximal ulna to avoid iatrogenic cartilage lesions.

OBJECTIVES

The goal of this study was to analyze the anatomy of the proximal ulna with regard to the bare area and, thereby, to optimize the hitting area of the bare area when performing olecranon osteotomy.

MATERIALS AND METHODS

The bare areas of 30 embalmed forearm specimens were marked with a radiopaque wire and visualized three-dimensionally with a mobile C‑arm. By means of 3D reconstructions of the data sets, the following measurements were obtained: height of the bare area; span of the bare area-hitting area in transverse osteotomy; ideal angle for olecranon osteotomy to maximize the hitting area of the bare area; distance of the posterior olecranon tip to the entry point of the transverse osteotomy and the ideal osteotomy.

RESULTS

The height of the bare area was 4.92 ± 0.81 mm. The hitting area of the transverse osteotomy averaged 3.73 ± 0.89 mm. The "ideal" angle for olecranon osteotomy was 30.7° ± 4.19°. The distance of the posterior olecranon tip to the entry point was 14.08 ± 2.75 mm for the transverse osteotomy and 24.21 ± 3.15 mm for the ideal osteotomy. The hitting area of the bare area in the ideal osteotomy was enhanced significantly when compared to the transverse osteotomy (p < 0.0001).

CONCLUSIONS

This study provides guide values for correct osteotomy of the olecranon. Moreover, a 30° angulation of the osteotomy can significantly increase the hitting area of the bare area.

Valgus Extension Overload in Baseball Players

Repetitive throwing, such as in baseball pitching, applies massive stress on the elbow. This can often lead to a predictable constellation of elbow injuries, such as valgus extension overload syndrome (VEO). The following review of VEO provides an understanding of relevant anatomy, explanation of pathomechanics, key aspects to clinical evaluation, effective treatment options, and indications for surgery. In addition, we provide the senior author's (CSA) preferred arthroscopic technique for cases of VEO refractory to conservative management.

Adaptive Control of Exoskeleton Robots for Periodic Assistive Behaviours Based on EMG Feedback Minimisation

In this paper we propose an exoskeleton control method for adaptive learning of assistive joint torque profiles in periodic tasks. We use human muscle activity as feedback to adapt the assistive joint torque behaviour in a way that the muscle activity is minimised. The user can then relax while the exoskeleton takes over the task execution. If the task is altered and the existing assistive behaviour becomes inadequate, the exoskeleton gradually adapts to the new task execution so that the increased muscle activity caused by the new desired task can be reduced. The advantage of the proposed method is that it does not require biomechanical or dynamical models. Our proposed learning system uses Dynamical Movement Primitives (DMPs) as a trajectory generator and parameters of DMPs are modulated using Locally Weighted Regression. Then, the learning system is combined with adaptive oscillators that determine the phase and frequency of motion according to measured Electromyography (EMG) signals. We tested the method with real robot experiments where subjects wearing an elbow exoskeleton had to move an object of an unknown mass according to a predefined reference motion. We further evaluated the proposed approach on a whole-arm exoskeleton to show that it is able to adaptively derive assistive torques even for multiple-joint motion.

The ulnar greater sigmoid notch "coverage angle": bone and cartilage contribution. Magnetic resonance imaging anatomic study on 78 elbows

BACKGROUND

To study the degree of coverage provided by the greater sigmoid notch (GSN) to the humeral trochlea, as well as the contribution of the olecranon and coronoid process cartilage tips to this angle, and its variations.

METHODS

We recruited 39 healthy volunteers, comprising 19 women and 20 men, with a mean age of 28 years (range, 21-32 years). High-definition magnetic resonance images were obtained for the right and left elbows. Four angles were measured on the sagittal plane passing through the coronoid and olecranon tips: angle A, identified by 2 lines from the trochlea center to the olecranon bone-cartilage junction and olecranon cartilage tip; angle B, identified by 2 lines from the trochlea center to the olecranon and coronoid bone-cartilage junction; angle C, identified by 2 lines from the trochlea center to the coronoid bone-cartilage junction and coronoid cartilage tip; and GSN coverage angle (GSN-ca), defined as the sum of angles A, B, and C. Pearson correlation tests, t tests, and intraclass correlation coefficients were used for statistical analyses.

RESULTS

The mean angle A, angle B, and angle C values were 6° (range, 2°-12°), 182° (range, 153°-204°), and 9° (range, 2°-16°), respectively. No correlations were found between these 3 angles. The mean GSN-ca was 198° (range, 167°-222°), and the GSN-ca was less than 180° in 8% of the cases. No significant differences emerged for side or gender or for total length of the ulna.

CONCLUSION

The GSN showed significantly different shapes on the sagittal plane that we defined as closed type when the GSN-ca was greater than 180° (92%) and as open type when the GSA-ca was less than 180° (8%). The cartilage tip contribution varied and was not correlated with that of bone.

The extended medial elbow approach-a cadaveric study

BACKGROUND

The two most commonly used approaches to expose medial elbow structures are the flexor carpi ulnaris split and the Hotchkiss over-the-top approach. The aim of this study was to define the extended medial approach to the elbow, featuring advantages of over-the-top (proximal exposure) and additional complete exposure of the coronoid and proximal medial ulna, while respecting the internervous plane between the flexor pronator mass and flexor carpi ulnaris muscle.

METHODS

In this comparative anatomic study, 12 fresh frozen cadaveric elbows were dissected alternately to study the distal limitation and exposed area of the extended medial elbow approach compared with splitting the flexor carpi ulnaris.

RESULTS

Proximal ulna exposure area was comparable between the extended medial elbow approach (average, 840 mm(2)) and the flexor carpi ulnaris split (average, 810 mm(2); P = .44). The extended medial approach was limited distally by the posterior recurrent ulnar artery (mean 68 mm from medial epicondyle), whereas the first motor branch for the flexor carpi ulnaris muscle limited the second approach in 75% of the specimens (mean 29 mm from medial epicondyle, P < .001).

CONCLUSIONS

The extended medial elbow approach is a single approach allowing full exposure of the medial elbow and combining the advantages of the over-the-top approach with a safe distal extension to the medial ulna. In contrast to the flexor carpi ulnaris split, our approach respects the internervous plane.

[Elbow tendinopathy]

The lateral and medial epicondylitis is often manifested in a professional or in a sport context leading to repetitive wrist movements. The diagnosis is primarily clinical. Additional tests are indicated in chronic evolution and in searching for differential diagnoses. Elbow X-ray can be completed with ultrasound or MRI, the most efficient but expensive diagnostic procedure. There is no consensus on treatment. After a period of rest, stretching then strengthening exercises are recommended. Corticosteroid injections may provide a short-term beneficial effect. Platelet-Rich Plasma injections have recently gained notoriety. In case of failure of treatment, surgery is possible, but only in a minority of patients.

A sonographic technique to evaluate the anterior bundle of the ulnar collateral ligament of the elbow: imaging features and anatomic correlation

OBJECTIVES

The aim of this study was to test a sonographic technique used to view the anterior bundle of the ulnar collateral ligament (UCL), describe its sonographic characteristics in healthy volunteers, and verify these characteristics by determining interobserver variability and their correlations in cadavers.

METHODS

Sonographic studies of the anterior bundle of the UCL were performed on 48 elbows of asymptomatic healthy volunteers. The participants were examined by 3 experts, who identified the insertion sites of the anterior bundle and subjectively evaluated its echogenicity and echo texture. A sonographic examination of the anterior bundle of the UCL in a cadaveric elbow was performed, and the same aspects were evaluated.

RESULTS

In all cases, the anterior bundle of the UCL appeared as a triangular structure in the coronal plane and had a hyperechoic homogeneous echo texture in most of these cases. The cadaveric elbow had the same sonographic characteristics as the volunteers.

CONCLUSIONS

As shown by examining the interobserver variability and determining the correlation with cadaveric tissue, sonography proved to be a reliable tool for evaluating the normal aspects of the anterior bundle of the UCL.

The Electrodiagnosis of Ulnar Nerve Entrapment at the Elbow

Entrapment of the ulnar nerve at the elbow is the second most common focal peripheral neuropathy. Recent advances have facilitated the electrodiagnosis of this common nerve entrapment. The goals of electrodiagnosis are to localize ulnar nerve dysfunction, confirm that the disturbance is confined to the ulnar nerve, and assess the severity of ulnar nerve dysfunction. The goal of this review is to highlight the important advances in anatomy, neurophysiology and methodology that impact upon the electrodiagnosis of entrapment of the ulnar nerve at the elbow, illustrate the limits of electrodiagnosis, and discuss methodological issues that may be the subject of further study. Careful attention to elbow position, temperature, and conservative estimates of conduction block should be part of common practice. Awareness of anatomical variations in structural anatomy, anomalous innervation and fascicular arrangement of ulnar nerve fibers are required to interpret electrodiagnostic studies accurately. The most reliable finding is slowing of the ulnar across-elbow motor nerve conduction velocity to less than 50 m/sec while recording from the abductor digiti minimi muscle, and should be carefully interpreted in the presence of a polyneuropathy or other neurogenic process. Alternative techniques such as relative ulnar slowing in different ulnar nerve segments, use of alternative muscles, sensory and mixed nerve techniques provide complementary information, and like all nerve conduction studies are highly operator-dependent and should be used on a case by case basis. Recent studies have focused the electromyographer's attention on the use of shorter across-elbow segments (2-5 cm). This may offer a reasonable trade-off between sensitivity and measurement error and may result in improved electrodiagnosis.

[Anatomical basis and clinical application of "two points" acupotomology surgery program in treating cubital tunnel syndrome]

OBJECTIVE

To explore an effective acupotomology surgery program in treating cubital tunnel syndrome.

METHODS

According to pathogenic factors and elbow anatomy, a "two points" acupotomology surgery program was designed, which could loose the attachment point of arcuate ligament on medial border of olecroanon and medial epicondyle of humerus. Twenty-one cases of cubital tunnel syndrome were treated with acupotmology, then the efficacy was obsered.

RESULTS

After one year postoperative visit, 21 patients with ulnar nerve area skin numbness were cured, claw hand deformity and medial hand muscle atrophy recovered significantly. Results of function evaluation were excellent in 17 cases, good in 2 cases, fair in 2 cases and poor in 0 cases, the good rate was 90.5%.

CONCLUSION

The acupotomology surgery program which could cut the starting and ending points of osborne's ligament and solve the problem of ulnar nerve entrapment is an easy, little-traumatic and effective minimally invasive surgery which also conforms to the anatomical structure.

The thrower's elbow

Overhead throwing activities expose the elbow to tremendous valgus stress, making athletes vulnerable to a specific constellation of injuries. Although baseball players, in particular pitchers, are the athletes affected most commonly, overhead throwing athletes in football, volleyball, tennis, and javelin tossing also are affected. The purpose of this review is to review the anatomy, biomechanics, pathophysiology, and treatment of elbow disorders related to overhead throwing athletes. Although focus is on management of ulnar collateral ligament injuries, all common pathologies are discussed.

Radial collateral ligament of the elbow: sonographic characterization with cadaveric dissection correlation and magnetic resonance arthrography

OBJECTIVES

An abnormality of the radial collateral ligament (RCL) in the setting of lateral epicondylitis can indicate a poor clinical outcome; therefore, accurate assessment is important. The purpose of this study was to characterize the proximal RCL attachment, or footprint, as seen on sonography using cadaveric dissection correlation and magnetic resonance arthrography.

METHODS

For the first part of this study, 4 cadaveric elbow specimens were imaged with sonography before and after dissection to characterize the RCL. After Institutional Review Board approval with consent waived, 26 consecutive magnetic resonance (MR) arthrograms of the elbow were identified. The sonograms and MR arthrograms were retrospectively reviewed to measure the length of the RCL footprint and its percentage of the combined RCL and common extensor tendon (CET) humeral footprints.

RESULTS

The mean RCL footprint length and percentage of the combined RCL and CET footprints were 8.4 mm (range, 7.4-10.0 mm) and 54% as measured from the elbow specimen sonograms and 9.1 mm (range, 6.4-12.5 mm) and 54% as measured from the MR arthrograms. The mean RCL footprint length combining data from specimens and MR arthrograms was 8.9 mm (range, 6.4-12.5 mm), covering 54% of the combined RCL and CET footprints.

CONCLUSIONS

The RCL can be differentiated from the CET on sonography with knowledge of the RCL humeral footprint extent, which measured 8.9 mm in length and comprised 54% of the combined RCL and CET footprints.

Biomechanics of forearm rotation: force and efficiency of pronator teres

Biomechanical models are useful to assess the effect of muscular forces on bone structure. Using skeletal remains, we analyze pronator teres rotational efficiency and its force components throughout the entire flexion-extension and pronation-supination ranges by means of a new biomechanical model and 3D imaging techniques, and we explore the relationship between these parameters and skeletal structure. The results show that maximal efficiency is the highest in full elbow flexion and is close to forearm neutral position for each elbow angle. The vertical component of pronator teres force is the highest among all components and is greater in pronation and elbow extension. The radial component becomes negative in pronation and reaches lower values as the elbow flexes. Both components could enhance radial curvature, especially in pronation. The model also enables to calculate efficiency and force components simulating changes in osteometric parameters. An increase of radial curvature improves efficiency and displaces the position where the radial component becomes negative towards the end of pronation. A more proximal location of pronator teres radial enthesis and a larger humeral medial epicondyle increase efficiency and displace the position where this component becomes negative towards forearm neutral position, which enhances radial curvature. Efficiency is also affected by medial epicondylar orientation and carrying angle. Moreover, reaching an object and bringing it close to the face in a close-to-neutral position improve efficiency and entail an equilibrium between the forces affecting the elbow joint stability. When the upper-limb skeleton is used in positions of low efficiency, implying unbalanced force components, it undergoes plastic changes, which improve these parameters. These findings are useful for studies on ergonomics and orthopaedics, and the model could also be applied to fossil primates in order to infer their locomotor form. Moreover, activity patterns in human ancient populations could be deduced from parameters reported here.

CT arthrography and anatomical correlation of the bare area of the ulnar trochlear fossa: a risk of misdiagnosis of cartilage ulcerations

AIMS

There is a variable bare area on the ulnar trochlear fossa that may be somehow interpreted as a cartilage defect. We aimed to correlate radiological images and dissections of this bare spot with CT arthrography imaging.

MATERIALS AND METHODS

We conducted a double study that included 10 unpaired fresh-frozen human cadaveric elbows (CT arthrography + dissection) and 40 CT arthrography of patients to investigate the 3-D architecture of the trochlear fossa of the ulna. Positioning, shape and measurements of the bare spot of each ulna were measured and correlated. A total of 40 were analyzed with this protocol of measurements to validate the anatomical findings.

RESULTS

The bare spot area is located 15.8 mm from the tip of the olecranon and 13.8 mm from the coronoid process (mean values). This area measures 4.1 mm in cranio-caudal plane, 2.2 mm in transversal plane. This area is located above a small subchondral tubercle that measures 1.0 mm in antero-posterior axis. No significant difference has been found between left and right elbow regarding its positioning and shape. A significant difference has been found between genders regarding the positioning of this area but not according to its shape.

CONCLUSION

The ulnar trochlear notch has a small area without cartilage. This bare area is located at the site of fusion of the different ossification center of the proximal ulna. It should not be interpreted as a chondral lesion. The existence of a subchondral tubercle clearly indicates that this uncovered zone is normal. Radiologist should consider this when interpreting elbow CT arthrography.

[Validation study on precision of digitized custom-made radial head prosthesis by three-dimensional visualization of virtual surgery]

OBJECTIVE

To study digitize design of custom-made radial head prosthesis and to verify its matching precision by the surgery of preoperative three-dimensional (3-D) virtual replacement.

METHODS

Six healthy adult volunteers (3 males and 3 females, aged 25-55 years with an average of 33 years) received slice scan of bilateral elbow by Speed Light 16-slice spiral CT. The CT Dicom data were imported into Mimics 10.0 software individually for 3-D reconstruction image, and the left proximal radial 3-D image was extracted, the mirror of the image was generated and it was split into 2 pieces: the head and the neck. The internal diameter and the length of the radial neck were obtained by Mimics 10.0 software measurement tools. In Geomagic Studio 12 software, the radial head was simulated to cover the cartilage surface (1 mm thickness) and generated to an entity. In UG NX 8.0 software, the stem of prosthesis was designed according to the parameters above and assembled head entity. Each custom-made prosthesis was performed and verified its matching precision by the surgery of preoperative 3-D virtual replacement.

RESULTS

Comparing the morphology of 6 digitize custom-made prostheses with ipsilateral radial heads by the 3-D virtual surgery, the error was less than 1 mm. The radial head prosthesis design on basis of the contralateral anatomy was verified excellent matching.

CONCLUSION

The 3-D virtual surgery test and the digitized custom-made radial head prosthesis will be available for clinical accurate replacement.

Relation of the radial nerve to the anterior capsule of the elbow: anatomy with correlation to arthroscopy

PURPOSE

To determine the location and proximity of the radial nerve to the anterior capsule and to delineate and describe the anatomy of the brachialis as it relates to the radial nerve and anterior capsule.

METHODS

Arthroscopy was performed on 24 cadavers using only a standard anteromedial portal. A Beath pin was placed laterally, entering the joint at the most lateral edge of the radiocapitellar joint space, and a suture was placed through the pin and into the joint for reference during the dissection. The second phase was to perform open anatomic dissections.

RESULTS

We found that in all specimens the radial nerve coursed longitudinally medial to the capitellum. The brachialis muscle was found to lie between the radial nerve and the joint capsule at the joint line and all proximal levels. Only at the most distal aspect of the joint line (corresponding to the level of the radial neck) did the nerve run in direct contact with the capsule in 11 specimens (55%). The brachialis muscle thickness was 4 mm or greater at the joint line and at all proximal measurement points.

CONCLUSIONS

We found that the radial nerve is more medially located than previously thought. At the level of the radiocapitellar joint line, the radial nerve runs medial to the capitellum. The brachialis muscle lies between the radial nerve and the joint capsule at the level of the joint line and proximally.

CLINICAL RELEVANCE

Arthroscopic capsular release laterally should be performed at the level of the joint line or above. The most dangerous area for capsular resection is distally over the radial head/neck, where 50% of our specimens had no brachialis protecting the nerve.

Similarities in the neural control of the shoulder and elbow joints belie their structural differences

Movement of the hand in three dimensional space is primarily controlled by the orientation of the shoulder and elbow complexes. Due to discrepancies in proprioceptive acuity, overlap in motor cortex representation and grossly different anatomies between these joints, we hypothesized that there would be differences in the accuracy of aimed movements between the two joints. Fifteen healthy young adults were tested under four conditions – shoulder motion with the elbow constrained and unconstrained, and elbow motion with the shoulder constrained and unconstrained. End point target locations for each joint were set to coincide with joint excursions of 10, 20 or 30 degrees of either the shoulder or elbow joint. Targets were presented in a virtual reality environment. For the constrained condition, there were no significant differences in angular errors between the two joints, suggesting that the central nervous system represents linked segment models of the limb in planning and controlling movements. For the unconstrained condition, although angle errors were higher, hand position errors remained the same as those of the constrained trials. These results support the idea that the CNS utilizes abundant degrees of freedom to compensate for the potentially different contributions to end-point errors introduced by each joint.

Elbow joint adductor moment arm as an indicator of forelimb posture in extinct quadrupedal tetrapods

Forelimb posture has been a controversial aspect of reconstructing locomotor behaviour in extinct quadrupedal tetrapods. This is partly owing to the qualitative and subjective nature of typical methods, which focus on bony articulations that are often ambiguous and unvalidated postural indicators. Here we outline a new, quantitatively based forelimb posture index that is applicable to a majority of extant tetrapods. By determining the degree of elbow joint adduction/abduction mobility in several tetrapods, the carpal flexor muscles were determined to also play a role as elbow adductors. Such adduction may play a major role during the stance phase in sprawling postures. This role is different from those of upright/sagittal and sloth-like creeping postures, which, respectively, depend more on elbow extensors and flexors. Our measurements of elbow muscle moment arms in 318 extant tetrapod skeletons (Lissamphibia, Synapsida and Reptilia: 33 major clades and 263 genera) revealed that sprawling, sagittal and creeping tetrapods, respectively, emphasize elbow adductor, extensor and flexor muscles. Furthermore, scansorial and non-scansorial taxa, respectively, emphasize flexors and extensors. Thus, forelimb postures of extinct tetrapods can be qualitatively classified based on our quantitative index. Using this method, we find that Triceratops (Ceratopsidae), Anhanguera (Pterosauria) and desmostylian mammals are categorized as upright/sagittally locomoting taxa.

Anatomic and biomechanical analysis of the short and long head components of the distal biceps tendon

HYPOTHESIS

The short head bundle of the distal biceps tendon is more efficient at elbow flexion, and the long head is more efficient at forearm supination.

METHODS

The short and long head bundles of the distal biceps tendon were separated to the bicipital tuberosity in 6 cadavers. The area and centroid of each bundle insertion were computed from surface points measured within each footprint. Each bundle was individually loaded. The supination torque and flexion load generated were recorded at 90° of elbow flexion. The slope of the torque generated versus biceps load was used to define the supination moment arm. The ratio of the flexion load generated to biceps load applied was used to define the relative flexion efficiency.

RESULTS

The short head insertion was positioned distal and anterior relative to the long head and typically included the apex of the tuberosity. The areas of the long and short heads were 59 ± 15 and 94 ± 44 mm(2) (P = .07), respectively. The long head moment arm was significantly higher in supination. The short head had a significantly higher moment arm in neutral and pronation. The ratio of the flexion load to biceps load was 15% higher for the short head.

CONCLUSION

The short and long heads of the biceps have distinct insertions. The short head's insertion allows it to be relatively more efficient at elbow flexion at 90°. In the neutral and pronated forearm, the short head is the relatively more efficient supinator. In the supinated forearm, the long head becomes relatively more efficient at supination.

Clinical working postures of bachelor of oral health students

OBJECTIVE

To observe and describe the clinical working postures of final-year Bachelor of Oral Health (BOH) students.

DESIGN

Pilot observational study.

SETTING

The University of Otago Faculty of Dentistry and School of Physiotherapy.

METHODS

Eight final-year BOH students voluntarily participated in this study, where postural data were collected using a digital video camera during a standard clinical treatment session. The postural data were analysed using 3D Match biomechanical software.

RESULTS

Final-year BOH students who work in the seated position are exposed to neck flexion of greater than 35 degrees, together with trunk flexion greater than 20 degrees and bilateral elbow flexion greater than 90 degrees.

CONCLUSIONS

The findings of this study agree with the findings of previous postural studies of dental professionals. Dental hygiene students, together with their clinical supervisors, need to be aware of the importance of good working posture early in their careers, and pay particular attention to the degree of neck flexion occurring for prolonged periods.

Topsy-turvy locomotion: biomechanical specializations of the elbow in suspended quadrupeds reflect inverted gravitational constraints

Some tetrapods hang upside down from tree branches when moving horizontally. The ability to walk in quadrupedal suspension has been acquired independently in at least 14 mammalian lineages. During the stance (supportive) phase of quadrupedal suspension, the elbow joint flexor muscles (not the extensors as in upright vertebrates moving overground) are expected to contract to maintain the flexed limb posture. Therefore muscular control in inverted, suspended quadrupeds may require changes of muscle control, and even morphologies, to conditions opposite to those in upright animals. However, the relationships between musculoskeletal morphologies and elbow joint postures during the stance phase in suspended quadrupeds have not been investigated. Our analysis comparing postures and skeletal morphologies in Choloepus (Pilosa), Pteropus (Chiroptera), Nycticebus (Primates) and Cynocephalus (Dermoptera) revealed that the elbow joints of these animals were kept at flexed angles of 70-100 ° during the stance phase of quadrupedal suspension. At these joint angles the moment arms of the elbow joint flexors were roughly maximized, optimizing that component of antigravity support. Our additional measurements from various mammalian species show that suspended quadrupeds have relatively small extensor/flexor ratios in both muscle masses and maximum moment arms. Thus, in contrast to the pattern in normal terrestrial quadrupeds, suspended quadrupeds emphasize flexor over extensor muscles for body support. This condition has evolved independently multiple times, attendant with a loss or reduction of the ability to move in normal upright postures.

[Magnetic resonance imaging elbow anatomy]

Knowledge of the anatomy of the elbow joint has become intricate due to the advent of magnetic resonance imaging (MRI) techniques, as they are superior to represent the different soft tissues. This advantage allows evaluating in detail the increasingly frequent pathologic processes that occur in high performance athletes. The ideal MRI technique includes having the patient in a comfortable position, using an appropriate surface antenna and the right sequences in the appropriate planes depending on the entity. Being familiar with the normal elbow anatomy is crucial to properly identify the pathology and avoid potential diagnostic errors.

The three-dimensional modeling of the complex virtual human elbow joint

The paper presents the algorithm to obtain a 3D virtual human elbow joint using CT images. For that purpose, we used CAD parametric software, which allows defining models with a high level of difficulty including complex 3D shapes. The virtual biomechanical system of the human elbow containing bones, ligaments and muscles is studied using the finite elements method and will be prepared for kinematical and dynamical simulations. The 3D virtual model will be useful for future studies concerning prosthesis optimization, improving the performances of endo-prosthetic and exo-prosthetic devices, different implants and prosthetic systems for normal and pathological situations, structures which are acted upon by SMA artificial muscles or which contain SMA elements.

Mono- versus biarticular muscle function in relation to speed and gait changes: in vivo analysis of the goat triceps brachii

The roles of muscles that span a single joint (monoarticular) versus those that span two (biarticular) or more joints have been suggested to differ. Monoarticular muscles are argued to perform work at a joint, whereas biarticular muscles are argued to transfer energy while resisting moments across adjacent joints. To test these predictions, in vivo patterns of muscle activation, strain, and strain rate were compared using electromyography and sonomicrometry in two major elbow extensors, the long and lateral heads of the triceps brachii of goats (Capra hircus), across a range of speed (1-5 m s(-1)) and gait. Muscle recordings were synchronized to limb kinematics using high-speed digital video imaging (250 Hz). Measurements obtained from four goats (25-45 kg) showed that the monoarticular lateral head exhibited a stretch-shortening pattern (6.8+/-0.6% stretch and -10.6+/-2.7% shortening; mean+/-s.e.m. for all speeds and gaits) after being activated, which parallels the flexion-extension pattern of the elbow. By contrast, the biarticular long head shortened through most of stance (-16.4+/-3.4%), despite elbow flexion in the first half and shoulder extension in the last half of stance. The magnitude of elbow flexion and shoulder extension increased with increasing speed (ANCOVA, P<0.05 and P<0.001), as did the magnitude and rate of active stretch of fascicles in the lateral head (P<0.001 for both). In all individuals, shortening fascicle strain rates increased with speed in the long head (P<0.001), and, in three of the four individuals, strain magnitude increased. Few independent effects of gait were found. In contrast to its expected function, the biarticular long head appears to produce positive work throughout stance, whereas the monoarticular lateral head appears to absorb work at the elbow. The biarticular anatomy of the long head may mitigate increases in muscle strain with speed in this muscle, because strain magnitude in the second phase of stance (when the shoulder extends) decreased with speed (P<0.05).

Surgical treatment of bicolumn distal humeral fractures: relevant anatomy and classification

Intercondylar or bicondylar distal humeral fractures involving both the medial and lateral columns are complex periarticular injuries that are challenging to treat. Understanding the normal elbow anatomy and classification systems that describe injury patterns provides the basis for the successful treatment of these complex humeral fractures.