Three-dimensional analysis of elbow soft tissue footprints and anatomy

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 joint capsule in the stability of the elbow joint

Existing studies lack a clear understanding of the interaction of the joint capsule with surrounding tissues and the local mechanical environment. Particularly, a finite element model of human elbow joint incorporating active behavior of muscle was constructed. The simulation was performed during the elbow joint flexion movement under different injury conditions of capsule (anterior capsule, posterior capsule, medial anterior capsule, lateral anterior capsule, medial posterior capsule, and lateral posterior capsule). The stress distribution and transfer of the joint capsule, ulnar cartilage, and ligaments were obtained under different injuries and flexion angles, to explore the influence of capsule injures on the stability of the elbow joint. In medial injury posterior capsule, the peak stress of the ulnar cartilage occurred at 60° flexion and shifted from posteromedial to anteromedial. And the stress was about 1.8 times that of no injury capsule. In several cases of posterior capsule injury, the stress of capsule decreased significantly and the peak stress was 40% of that in no injury joint capsule. In the case of anterior capsular injury, the cartilage stress did not change significantly, and the stress of anterior bundle and annular ligament changed slightly in the late flexion movement. These findings provide some help for doctors to treat elbow injury and understand the interaction of tissues around the joint after trauma.

Anatomic Study of the Medial Collateral Ligament in Thai Population: A Cadaveric Study of 56 Elbows

PURPOSE

This study aims to elucidate basic anatomic and geometric features of MCL, providing more accurate and detailed information, as guidance for surgeons, to improve patient's outcome of the treatment.

METHODS

The anterior bundle (AB), posterior bundle (PB) and transverse bundle (TB) ligament of 56 fresh frozen Thai cadaveric elbows, were measured and recorded, comprise key ligament's geometric features, footprints and dimensions, and its relation to bony landmarks. Sagittal and coronal planes were used in respect of the anatomical position.

RESULTS

The mean distance between the center of AB origin and the apex of medial epicondyle is as follows: 2.97 ± 2.21 mm anteriorly, 4.73 ± 1.60 mm inferiorly in the sagittal plane, and 4.23 ± 1.13 mm deep from the epicondyle in the coronal plane. Its dimension is 6.23 ± 1.02 mm in width and 45.97 ± 6.75 mm in length. The ligament's insertion triangular shape has its base located 28.44 ± 3.51 mm anterior from the posterior olecranon border, and 22.52 ± 2.49 mm superior from the inferior ulnar border. The tip located 50.79 ± 4.86 mm anterior from the posterior olecranon border and 17.64 ± 2.80 mm superior from the inferior ulnar border.

CONCLUSION

Apprehension of the precise geometries and distances of the ligament's footprint relative to key anatomical point is crucial. This stereographically comprehended data are useful for surgeon as reference points to obtain stability, motion, kinetic, and kinematic properties of the elbow.

LEVEL OF EVIDENCE

Level V evidence.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-022-00648-x.

Distal Triceps Tendon Tears: Magnetic Resonance Imaging Patterns Using a Systematic Classification

OBJECTIVE

This study aimed to evaluate distal triceps tendon tear patterns using a systematic classification based on the tendon's layered structure.

METHODS

We retrospectively identified Magnetic resonance imaging (MRI) examinations with triceps tendon tears that underwent reconstructive surgery. Magnetic resonance images were reviewed independently by 2 musculoskeletal radiologists to determine tendon layer involvement and ancillary findings, including tear size, involvement of triceps lateral expansion, and presence of olecranon bursal fluid. Surgical reports were scrutinized for level of anatomic detail and correlation with imaging findings.

RESULTS

We identified 69 triceps tendon tears in 68 subjects (61 men, 7 women; mean age, 45 ± 12 years) who underwent surgical reconstruction. On MRI, the superficial layer was always involved with either a partial or full-thickness tear. The most common tear pattern was a combination of superficial layer full-thickness tear with deep layer partial tear (25 of 69 [36%]). Mean tear length was 24 ± 12 mm. We found no cases of isolated deep layer tears. Involvement of triceps lateral expansion and presence of bursal fluid correlated positively with tear severity of superficial and deep layers (P < 0.001). Detailed surgical correlation was limited, with only 9 of 69 (13%) of surgical reports containing information specifically addressing individual tendon layers.

CONCLUSIONS

Triceps tendon tears show tear patterns following its layered structure and can be assessed by MRI. Radiologists and surgeons are encouraged to describe tear patterns considering both superficial and deep tendon layers.

Rehabilitation of Elbow Instability

The elbow is the second most commonly dislocated major joint in adults with estimated incidence of 5 dislocations per 100,000 persons per year. A comprehensive understanding of elbow anatomy and biomechanics is essential to optimize rehabilitation of elbow injuries. This allows for implementation of a systematic therapy program that encourages early mobilization within a safe arc of motion while maintaining joint stability. To optimize outcomes, close communication between surgeon and therapist is necessary to allow for implementation of an individualized rehabilitation program. This article reviews key concepts that enable the clinician to apply an evidence-informed approach when managing elbow instability.

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.

Distal Triceps Tendon Injuries

Distal triceps ruptures are uncommon, usually caused by a fall on an outstretched hand or a direct blow. Factors linked to injury include eccentric loading of a contracting triceps, anabolic steroid use, weightlifting, and traumatic laceration. Risk factors include local steroid injection, hyperparathyroidism, and olecranon bursitis. Initial diagnosis can be complicated by pain and swelling, and a palpable defect is not always present. Plain radiographs can be helpful. MRI confirms the diagnosis and directs treatment. Incomplete tears can be treated nonsurgically; complete tears are best managed surgically. Good to excellent restoration of function has been shown with surgical repair.

Anconeus-Sparing Minimally Invasive Approach for Lateral Ulnar Collateral Ligament Reconstruction in Posterolateral Elbow Instability

Posterolateral elbow instability with an insufficiency of the lateral ulnar collateral ligament commonly results from elbow trauma. However, other etiologies such as iatrogenic injuries after primary surgical treatment for lateral epicondylitis or repetitive corticosteroid injections also may lead to a lateral ulnar collateral ligament insufficiency. In these cases, surgical treatment can help to restore posterolateral stability of the elbow. Besides the stabilizing effect of the ligamentous structures, the anconeus muscle is the most import active stabilizer against posterolateral elbow instability. Therefore, the aim of the present technique is to present an anconeus-sparing, minimally invasive approach to restore posterolateral stability. This technique may serve as an alternative for typically used all open access.

Clinical Value of an Acute Popping Sensation in Throwing Athletes With Medial Elbow Pain for Ulnar Collateral Ligament Injury

Background:

Throwing athletes sustaining an ulnar collateral ligament (UCL) injury may recall a popping sensation originating from the medial elbow at the time of injury. There are no studies available that inform clinicians how to utilize this salient anamnestic information and what amount of diagnostic weight to afford to it.

Purpose:

To assess the diagnostic value of a popping sensation for significant UCL injury in throwing athletes who sustained an injury causing medial elbow pain.

Study Design:

Cohort study (prognosis); Level of evidence, 3.

Methods:

A total of 207 consecutive patients with throwing-related medial elbow pain were evaluated for UCL injury by the senior author between 2011 and 2016. The presence or absence of a popping sensation was routinely reported by the senior author. Magnetic resonance imaging was evaluated for UCL injury severity and classified into intact, edema/low-grade partial-, high-grade partial-, and full-thickness tears.

Results:

The overall frequency of a pop was 26%. The proportion of patients who reported a pop significantly increased with UCL tear severity (P < .001), from 13% in patients with low-grade UCL injuries to 26% in patients with high-grade partial-thickness tears and 51% in patients with full-thickness tears. The positive likelihood ratio, negative likelihood ratio, and odds ratio of a popping sensation for significant UCL injury were 3.2, 0.7, and 4.4 (P < .001), respectively (P < .001). A pop was not associated with either distal or proximal UCL tears (P ≥ .999).

Conclusion:

A popping sensation at the time of injury in throwing athletes with medial elbow pain was associated with UCL injury severity. When a throwing athlete reports a pop, this should moderately increase a clinician’s suspicion for a significant UCL injury. Conversely, absence of a pop should not substantially decrease suspicion for significant UCL injury. The findings of this study allow for the clinical interpretation of the salient anamnestic finding of a pop at the time of injury, which can be used for diagnostic purposes as well as patient counseling. This study provides reference foundation for future studies of predictive and diagnostic factors for UCL injury in throwing athletes.

Anatomic and Biomechanical Evaluation of Ulnar Tunnel Position in Medial Ulnar Collateral Ligament Reconstruction

BACKGROUND

Although numerous techniques of reconstruction of the medial ulnar collateral ligament (mUCL) have been described, limited evidence exists on the biomechanical implication of changing the ulnar tunnel position despite the fact that more recent literature has clarified that the ulnar footprint extends more distally than was appreciated in the past.

PURPOSE

To evaluate the size and location of the native ulnar footprint and assess valgus stability of the medial elbow after UCL reconstruction at 3 ulnar tunnel locations.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. The anatomic footprint of the ulnar attachment of the mUCL was measured with a digitizing probe. The area of the ulnar footprint and midpoint relative to the joint line were determined. Medial elbow stability was tested with the mUCL in an intact, deficient, and reconstructed state after the docking technique, with ulnar tunnels placed at 5, 10, or 15 mm from the ulnotrochlear joint line. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion-tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, specimens were loaded to failure at 70° of elbow flexion.

RESULTS

The mean ± SD length of the mUCL ulnar footprint was 27.4 ± 3.3 mm. The midpoint of the anatomic footprint was located between the 10- and 15-mm tunnels across all specimens at a mean 13.6 mm from the joint line. Sectioning of the mUCL increased elbow valgus rotation throughout all flexion angles and was statistically significant from 30° to 100° of flexion as compared with the intact elbow (P < .05). mUCL reconstruction at all 3 tunnel locations restored stability to near intact levels with no significant differences among the 3 ulnar tunnel locations at any flexion angle.

CONCLUSION

Positioning the ulnar graft fixation site up to 15 mm from the ulnotrochlear joint line does not significantly increase valgus rotation in the elbow.

CLINICAL RELEVANCE

A more distal ulnar tunnel may be a viable option to accommodate individual variation in morphology of the proximal ulna or in a revision setting.

Variation of the clavicle's muscle insertion footprints - a cadaveric study

The muscle footprint anatomy of the clavicle is described in various anatomical textbooks but research on the footprint variation is rare. Our goal was to assess the variation and to create a probabilistic atlas of the muscle footprint anatomy. 14 right and left clavicles of anatomical specimens were dissected until only muscle fibers remained. 3D models with muscle footprints were made through CT scanning, laser scanning and photogrammetry. Then, for each side, the mean clavicle was calculated and non-rigidly registered to all other cadaveric bones. Muscle footprints were indicated on the mean left and right clavicle through the 1-to-1 mesh correspondence which is achieved by non-rigid registration. Lastly, 2 probabilistic atlases from the clavicle muscle footprints were generated. There was no statistical significant difference between the surface area (absolute and relative), of the originally dissected muscle footprints, of male and female, and left and right anatomical specimens. Visualization of all muscle footprints on the mean clavicle resulted in 72% (right) and 82% (left) coverage of the surface. The Muscle Insertion Footprint of each specimen covered on average 36.9% of the average right and 37.0% of the average left clavicle. The difference between surface coverage by all MIF and the mean surface coverage, shows that the MIF location varies strongly. From the probabilistic atlas we can conclude that no universal clavicle exists. Therefore, patient-specific clavicle fracture fixation plates should be considered to minimally interfere with the MIF. Therefore, patient-specific clavicle fracture fixation plates which minimally interfere with the footprints should be considered.

The naked capitellum: a surgeon's guide to intraoperative identification of posterolateral rotatory instability

HYPOTHESIS

This study's purpose was to provide a reproducible way for surgeons to intraoperatively assess the elbow's lateral ulnar collateral ligament origin and determine whether there is posterolateral rotatory instability (PLRI) despite an intact common extensor origin (CEO). We hypothesized that we could re-create clinically relevant disruption of lateral supporting structures despite an intact CEO and illustrate progressive elbow PLRI.

METHODS

The relationship of the lateral capsule to the capitellum articular surface was noted in 8 cadaveric upper extremities. The lateral capsule and extensor origin were sequentially sectioned at 4 stages: intact, release to the lateral epicondyle, release of the posterior capsular insertion, and release of the CEO. Posterior and lateral translation of the radial head (RH) relative to the capitellum was measured with the forearm in extension and supination.

RESULTS

The average specimen age was 78.9 years. The lateral capsule originated within 1 to 2 mm of the capitellum articular surface. Lateral capsular sectioning to the 6-o'clock position of the lateral epicondyle created an unstable elbow with posterior and lateral RH translation. Sequential sectioning of the posterior capsular insertion created significant additional RH translation posteriorly (P < .05). With release of the capsule and the extensor origin, the elbow was grossly unstable.

CONCLUSIONS

The elbow's lateral capsuloligamentous complex plays an important role in preventing PLRI. Larger degrees of elbow laxity are associated with further peel back of the capsuloligamentous complex despite an intact CEO. The surgeon must retract the extensor origin intraoperatively to assess for lateral ulnar collateral ligament and/or lateral capsule disruption to prevent a missed case of PLRI.

Quantifying the Center of Elbow Rotation: Implications for Medial Collateral Ligament Reconstruction

BACKGROUND

Medial collateral ligament (MCL) reconstruction of the elbow mandates precise characterization of where the centerline of elbow rotation projects onto the medial epicondyle (ME). A muscle-splitting approach allows the flexor-pronator muscles to remain attached to the ME and facilitates visualization of the MCL remnant, the sublime tubercle, and the ulnohumeral joint line. Knowledge of where the centerline of rotation intersects the ME relative to the ulnohumeral joint line may assist the surgeon during placement of the proximal drill hole.

METHODS

Models were created from the computed tomography scans of 29 normal elbows. The centerline of rotation, center of the trochlea, sublime tubercle, and ulnohumeral joint line were identified. Measurements were taken from the ulnohumeral joint line to the center of the trochlea and to the centerline of rotation in the sagittal view and along the course of the MCL.

RESULTS

The centerline of rotation intersected the ME in a consistent location. With the elbow flexed 90°, the trochlea center and the centerline of rotation are essentially in line with each other. There are significant differences between the distances from the ulnohumeral joint line to the center of the trochlea and to the centerline of rotation in both the sagittal view and along the course of the MCL.

CONCLUSIONS

The centerline of rotation is located 14.31 mm (1.70) from the ulnohumeral joint line in the sagittal view and 16.54 mm (2.09) from the ulnohumeral joint line along the course of the MCL.

The V-Shaped Distal Triceps Tendon Repair: A Comparative Biomechanical Analysis

BACKGROUND

Restoring footprint anatomy, minimizing gap formation, and maximizing the strength of distal triceps tendon repairs are essential factors for a successful healing process and return to sport.

HYPOTHESIS

The novel V-shaped distal triceps tendon repair technique with unicortical button fixation closely restores footprint anatomy, provides minimal gap formation and high ultimate failure load, and minimizes iatrogenic fracture risk in acute/subacute distal triceps tendon tears.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-four cadaveric elbows (mean ± SD age, 66 ± 5 years) were randomly assigned to 1 of 3 repair groups: the transosseous cruciate repair technique (gold standard), the knotless suture-bridge repair technique, and the V-shaped distal triceps tendon repair technique. Anatomic measurements of the central triceps tendon footprint were obtained in all specimens with a 3-dimensional digitizer before and after the repair. Cyclic loading was performed for a total of 1500 cycles at a rate of 0.25 Hz, pulling in the direction of the triceps. Displacements were measured on the medial and lateral tendon sites with 2 differential variable reluctance transducers. Load to failure and construct failure mode were recorded.

RESULTS

The mean triceps bony insertion area was 399.05 ± 81.23 mm². The transosseous cruciate repair technique restored 36.6% ± 16.8% of the native tendon insertion area, which was significantly different when compared with the knotless suture-bridge repair technique (85.2% ± 14.8%, P = .001) and the V-shaped distal triceps tendon repair technique (88.9% ± 14.8%, P = .002). Mean displacement showed no significant difference between the V-shaped distal triceps tendon repair technique (medial side, 0.75 ± 0.56 mm; lateral side, 0.99 ± 0.59 mm) and the knotless suture-bridge repair technique (1.61 ± 0.97 mm and 1.29 ± 0.8 mm) but significance between the V-shaped distal triceps tendon repair technique and the transosseous cruciate repair technique (4.91 ± 1.12 mm and 5.78 ± 0.9 mm, P < .001). Mean peak failure load of the V-shaped distal triceps tendon repair technique (732.1 ± 156.0 N) was significantly higher than that of the knotless suture-bridge repair technique (505.4 ± 173.9 N, P = .011) and the transosseous cruciate repair technique (281.1 ± 74.8 N, P < .001). Mechanism of failure differed among the 3 repairs, with the only olecranon fracture occurring in the knotless suture-bridge repair technique at the level of the lateral row suture anchors.

CONCLUSION

At time zero, the V-shaped distal triceps tendon repair technique and the knotless suture-bridge repair technique both provided anatomic footprint coverage. Ultimate load to failure was highest for the V-shaped distal triceps tendon repair technique, while gap formation was different only in comparison with the transosseous cruciate repair technique.

CLINICAL RELEVANCE

The V-shaped distal triceps tendon repair technique provides an alternative procedure to other established repairs for acute/subacute distal triceps tendon ruptures. The reduced repair site motion of the V-shaped distal triceps tendon repair technique and the knotless suture-bridge repair technique at the time of surgery may allow a more aggressive rehabilitation program in the early postoperative period.

Quantitative Anatomic Analysis of the Medial Ulnar Collateral Ligament Complex of the Elbow

Background

A more detailed assessment of the anatomy of the entire medial ulnar collateral ligament complex (MUCLC) is desired as the rate of medial elbow reconstruction surgery continues to rise.

Purpose

To quantify the anatomy of the MUCLC, including the anterior bundle (AB), posterior bundle (PB), and transverse ligament (TL).

Study Design

Descriptive laboratory study.

Methods

Ten unpaired, fresh-frozen cadaveric elbows underwent 3-dimensional (3D) digitization and computed tomography with 3D reconstruction. Ligament footprint areas and geometries, distances to key bony landmarks, and isometry were determined. A surgeon digitized the visual center of each footprint, and this location was compared with the geometric centroid calculated from the outline of the digitized footprint.

Results

The mean surface area of the AB was 324.2 mm², with an origin footprint of 32.3 mm² and an elongated insertional footprint of 187.6 mm² (length, 29.7 mm). The mean area of the PB was 116.6 mm² (origin, 25.9 mm²; insertion, 15.8 mm²), and the mean surface area of the TL was 134.5 mm² (origin, 21.2 mm²; insertion, 16.7 mm²). The geometric centroids of all footprints could be predicted within 0.8 to 1.3 mm, with the exception of the AB insertion centroid, which was 7.6 mm distal to the perceived center at the apex of the sublime tubercle. While the PB remained relatively isometric from 0° to 90° of flexion (P = .606), the AB lengthened by 2.2 mm (P < .001).

Conclusion

Contrary to several historical reports, the insertional footprint of the AB was larger, elongated, and tapered. The TL demonstrated a previously unrecognized expansive soft tissue insertion directly onto the AB, and additional analysis of the biomechanical contribution of this structure is needed.

Clinical Relevance

These findings may serve as a foundation for future study of the MUCLC and help refine current surgical reconstruction techniques.

Functional outcomes following lateral ulnar collateral ligament reconstruction for symptomatic posterolateral rotatory instability of the elbow in an athletic population

HYPOTHESIS

The purpose of this investigation was to characterize the functional and surgical outcomes following lateral ulnar collateral ligament (LUCL) reconstruction for posterolateral rotatory instability in an athletic population.

METHODS

All US military service members who underwent LUCL reconstruction between 2008 and 2013 were identified. A retrospective chart review was performed, and the prospective Mayo Elbow Performance Score and QuickDASH (short version of Disabilities of the Arm, Shoulder and Hand questionnaire) score were obtained. The primary outcomes were return to preinjury activity and resolution of symptoms.

RESULTS

We identified 23 patients with a mean age of 31.6 ± 7.2 years (range, 19-46 years), and 87% were men. A history of instability and/or dislocation was reported by 11 patients (48%), and 8 patients (35%) had undergone prior elbow surgery. At final follow-up of 4.6 ± 1.8 years (range, 2.2-7.6 years), all patients demonstrated significant decreases in pain (average pain score, 4 vs 1.34) with resolution of instability and achieved a functional arc of motion. After surgical reconstruction, 83% were able to return to prior activity, whereas 4 patients (17%) underwent medical separation, including 3 with elbow disability precluding continued service (13%). Overall 83% of patients reported good to excellent outcomes by the Mayo Elbow Performance Score, and 96% of patients reported no significant disability by the QuickDASH disability evaluation. Postoperatively, 4 patients (17%) experienced complications, with 3 (13%) requiring reoperation.

CONCLUSION

Although the diagnosis and surgical management of isolated LUCL injury are relatively infrequent, LUCL reconstruction for posterolateral rotatory instability offers a reliable return to preinjury level of function among active individuals with intense upper extremity demands. However, although function reliably improves, the rate of perioperative complications is greater than 15%.

Head-shaft angle changes during internal and external shoulder rotations: 2-D angulation in 3-D space

INTRODUCTION

Restoration of native head-shaft angle (HSA) is critical for treatment of proximal humerus fracture. However, HSA has not been properly investigated according to the humeral rotation. This study was designed to analyze the relationship between the humeral rotation and the HSA at 1° increments, and clarify its serial changing pattern according to the humeral rotation.

HYPOTHESIS

The angulation of HSA would be undervalued when the humerus is being rotated externally and it would be overvalued when it is being rotated internally.

MATERIALS AND METHODS

Eight dried cadaveric normal humeri were CT scanned. They were analyzed using computer-aided design with a standardized neutral position. HSA was the angle between the humeral shaft axis (SA) and the humeral head axis (HA). SA and HA were the best-fit lines through center of all the best-fitting circles in every cross section along the humeral shaft and within the humeral head, respectively. Each 3D model was rotated 30° internally and 45° externally relatives to the SA at 1° increments with the camera was fixed at antero-posterior view of neutral position. Angulation of HSA in every rotational degree was documented as ratio relatives to the angulation of HSA in neutral position.

RESULTS

The average HSA at neutral position was 133±1.93°. HSA was underestimated by 8±1.9% and it was overestimated by 20±5.1% at the maximum external rotation (ER) and internal rotation (IR), respectively. HSA was underestimated by 1% in every 5.8° of ER and overestimated by 1% in every 1.5° of IR. Rotational misalignments within 10° of IR and 18° of ER could be tolerated (P>.05).

CONCLUSIONS

HSA was underestimated at ER and was overestimated at IR. This information could be useful for surgeons in restoring the native HSA for treatment of proximal humerus fracture.

TYPE OF STUDY

Basic research study.

Distal Triceps Tendon Injuries

Acute triceps ruptures are an uncommon entity, occurring mainly in athletes, weight lifters (especially those taking anabolic steroids), and following elbow trauma. Accurate diagnosis is made clinically, although MRI may aid in confirmation and surgical planning. Acute ruptures are classified on an anatomic basis based on tear location and the degree of tendon involvement. Most complete tears are treated surgically in medically fit patients. Partial-thickness tears are managed according to the tear severity, functional demands, and response to conservative treatment. We favor an anatomic footprint repair of the triceps to provide optimal tendon to bone healing and, ultimately, functional outcome.

Elbow US: Anatomy, Variants, and Scanning Technique

As with other musculoskeletal joints, elbow ultrasonography (US) depends on the examination technique. Deep knowledge of the relevant anatomy, such as the bone surface anatomy, tendon orientation, nerves, and vessels, is crucial for diagnosis. It is important to be aware of the primary imaging pitfalls related to US technique (anisotropy) in the evaluation of deep tendons such as the distal biceps and peripheral nerves. In this article, US scanning technique for the elbow as well as the related anatomy, primary variants, and scanning pitfalls are described. In addition, an online video tutorial of elbow US describes a possible approach to elbow evaluation. Online supplemental material is available for this article.