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

Morphometric analysis of the lateral column of the distal humerus with an interest on radio-capitellar arthroplasty design. A computed tomography anatomical study on 50 elbows

PURPOSE

To perform a morphometric analysis of the distal humerus lateral column medullary canal (LCMC).

METHODS

Fifty computed tomography(CTs) from 24 males and 26 females were examined. Two observers measured: (1) the capitellum sagittal (R_S) and axial (R_T) radii of curvature; (2) the sagittal(Sd) and coronal(Cd) diameters of the LCMC in 5 different disto-proximal sites spaced 4 mm apart; (3) the capitellum and LCMC axis offsets on the sagittal (capSO,axSO) and coronal (capCO,axCO) planes; (4) the sagittal (Si) and coronal (Ci) inclination of the LCMC axis.

RESULTS

The mean R_S and R_T were 1.07 cm (SD, 0.11) and 1.30 cm (SD, 0.11), respectively. The mean Sd and Cd values were 1.17 cm (SD, 0.17) and 1.58 cm (SD, 0.24), respectively, with a disto-proximal decrease on both planes. The capSO, capCO, axSO and axCO mean values were 0.76 (SD, 0.21), 1.60 (SD, 0.27), - 0.16 (SD, 0.30) and 0.79 cm (SD, 0.30), respectively. Si and Ci were 70° and 72°, respectively. A strong correlation (r = 0.78) was found between R_S and R_T and between adjacent levels of Sd and Cd. AxSO and axCO yielded a strong inverse correlation. Male patients showed higher values than female ones in all variables (p < 0.03). The intra-class correlation coefficient (ICC) was always > 0.9.

CONCLUSION

The dimensions of the LCMC decrease disto-proximally, with the coronal diameters being greater than the sagittal diameters, resembling a portion of an elliptic torus with an antero-medial concavity. The articular surface of the humeral capitellum is non-spherical, with two strongly correlated radii of curvature. The results of this study may be relevant to the stem design of radiocapitellar arthroplasty.

Distal Humeral Trochlear Geometry Associated With the Spatial Variation of the Dynamic Elbow Flexion Axis

Background: The complexity of the spatial dynamic flexion axis (DFA) of the elbow joint makes the elbow prosthesis design and humeral component alignment challenging. This study aimed to 1) investigate the variations of the spatial DFA during elbow flexion and 2) investigate the relationship between the distal humeral trochlear geometry and the in vivo spatial variation of the DFA.

Methods: Ten healthy subjects participated in this study. Each subject performed a full elbow extension to maximum flexion with hand supination under dual fluoroscopic imaging system (DFIS) surveillance. The 2D fluoroscopic images and the 3D bone models were registered to analyze the in vivo elbow kinematics and DFAs. The spatial DFA positions were defined as inclination with the medial and lateral epicondyle axes (MLA) in the transverse and coronal planes. The range of the DFA positions was also investigated during different flexion phases. The Spearman correlation method was used to analyze the relationship between the distal humeral trochlear’s morphological parameters and the position of DFAs during different flexion phases.

Results: The pathway of the DFAs showed an irregular pattern and presented individual features. The medial trochlear depth (MTD) (r = 0.68, p = 0.03) was positively correlated with the range of the DFA position (2.8° ± 1.9°) in the coronal plane from full extension to 30° of flexion. Lateral trochlear height (LTH) (r = −0.64, p = 0.04) was negatively correlated with the DFA position (−1.4° ± 3.3°) in the transverse plane from 30° to 60° of flexion. A significant correlation was found between LTH with the DFA position in the coronal (r = −0.77, p = 0.01) and transverse planes (r = −0.76, p = 0.01) from 60° to 90° of flexion.

Conclusion: This study showed that the pathway of the dynamic flexion axis has an individual pattern. The medial and lateral trochlear sizes were the key parameters that might affect the elbow joint flexion function. When recovering complex distal humeral fractures or considering the implant design of total elbow arthroplasty, surgeons should pay more attention to the medial and lateral trochlea’s geometry, which may help restore normal elbow kinematics.

The inter-individual anatomical variation of the trochlear notch as a predisposition for simple elbow dislocation

PURPOSE

Besides the multi-layered capsule-ligamentous complex of the elbow joint the high bony congruence in the ulnohumeral joint contributes to elbow stability. Therefore, we assume that specific anatomical configurations of the trochlear notch predispose to dislocation. In case of ligamentous elbow dislocation both conservative and surgical treatment is possible without a clear treatment algorithm. Findings of constitutional bony configurations could help deciding for the best treatment option.

METHODS

In this retrospective matched-pair analysis we compared MRI imaging from patients sustaining a primary traumatic elbow dislocation (instability group) with patients suffering from chronic lateral epicondylitis (control group), treated between 2009 and 2019. Two independent observers measured different anatomical landmarks of the trochlear notch in a multiplanar reconstructed standardized sagittal trochlear plane (SSTP). Primarily, opening angle and relative depth of the trochlear notch were determined. After adjustment to the proximal ulnar rim in the SSTP, coronoid and olecranon angle, the articular angle as well as the ratio of the tip heights of the trochlear notch were measured.

RESULTS

We compared 34 patients in the instability group (age 48 ± 14 years, f/m 19/15) with 34 patients in the control group (age 47 ± 16 years, f/m 19/15). Instability group showed a significantly larger opening angle (94.1° ± 6.9° vs. 88.5° ± 6.9°, p = 0.0002), olecranon angle (60.9° ± 5.3° vs. 56.1° ± 5.1°, p < 0.0001) and articular angle (24.7° ± 6.4° vs. 22.3° ± 5.8°, p = 0.02) compared to the control group. Measuring the height from the coronoid (ch) and olecranon (oh) tip also revealed a significantly larger tip ratio (tr = ch/oh) in the instability group (2.7 ± 0.8 vs. 2.2 ± 0.5, p < 0.0001). The relative depth (61.0% ± 8.3% vs. 62.7% ± 6.0%, p = 0.21) of the trochlear notch as well as the coronoid angle (32.8° ± 4.5° vs. 31.7° ± 5.2°, p = 0.30) showed no significant difference in the instability group compared to the control group. The interrater reliability of all measurements was between 0.83 and 0.94.

CONCLUSION

MRI of patients with elbow dislocation show that there seems to be a bony anatomical predisposition. According to the results, it seems reasonable to include predisposing bony factors in the decision-making process when surgical stabilization and conservative treatment is possible. Further biomechanical studies should prove these assumptions to generate critical bony values helping surgeons with decision making.

LEVEL OF EVIDENCE

III.

Clinical anatomy and biomechanics of the elbow

The anatomy of the elbow joint had been studied extensively over the last 2 decades. The increased understanding of the anatomy and contribution of the anatomical structures to the elbow biomechanics had enabled surgeons to improve the results of surgical reconstruction and fracture fixation. This review articles intend to summarise the salient functional and clinical anatomical and relevant biomechanical data that had been published recently.

Magnetic resonance imaging of the elbow

Elbow pain can cause disability, especially in athletes, and is a common clinical complaint for both the general practitioner and the orthopaedic surgeon. Magnetic resonance imaging (MRI) is an excellent tool for the evaluation of joint pathology due to its high sensitivity as a result of high contrast resolution for soft tissues. This article aims to describe the normal imaging anatomy and biomechanics of the elbow, the most commonly used MRI protocols and techniques, and common MRI findings related to tendinopathy, ligamentous and osteochondral injuries, and instability of the elbow.

Lateral Trochlear Ridge: A Non-Articulating Zone for Anterior-to-Posterior Screw Placement in Fractures Involving the Capitellum and Trochlea

BACKGROUND

Coronal shear fractures of the distal aspect of the humerus that involve the capitellum and the trochlea are rare; nevertheless, they are difficult to treat because of the complex fracture patterns and osteochondral nature of the fragments, limiting optimal screw placement. The use of anterior-to-posterior screw fixation by a lag technique (without countersinking) could potentially improve the strength of the construct. Our primary research question was to anatomically determine if there is a non-articulating zone for screw placement along the anterior aspect of the lateral trochlear ridge (aLTR) throughout normal elbow range of motion.

METHODS

Eight fresh-frozen cadaveric elbows were used. The region of interest was defined with 3 polymeric pins inserted in the inferior, middle, and superior-most aspects of the aLTR of each elbow, with use of an extensor digitorum communis (EDC) split approach. The elbows were then mounted on a magnetic resonance imaging (MRI)-compatible compression frame and subjected to high-resolution 7-T MRI at 90°, 120°, and 145° of flexion (positions of potential impingement), and at neutral and maximal pronation and maximal supination for each position of flexion. Portions of the aLTR that had free adjacent space were identified using the sagittal and coronal scans. This non-articulating region was identified as the "non-articulating zone" (NAZ).

RESULTS

The NAZ was found to encompass the proximal 38.2% (range, 30.2% to 48.9%) of the aLTR, measuring, on average, 5.2 mm in width. It was consistently located either directly adjacent to the apex of the ridge or just medial to it. The distal 61.8% of the aLTR articulated with either the ulna or the radial head in some of the elbows.

CONCLUSIONS

Our results suggest that there is a portion of the aLTR that, despite being covered with articular cartilage, is non-articulating throughout normal elbow range of motion.

CLINICAL RELEVANCE

In situations in which headless anterior-to-posterior and posterior-to-anterior screw insertion results in inadequate fixation of capitellar-trochlear fractures, anterior-to-posterior lag screw instrumentation along the non-articulating portion of the aLTR may provide a location for additional fixation in some patients. However, because of variation between patients, each case must be individualized.

Regional Distribution of Articular Cartilage Thickness in the Elbow Joint: A 3-Dimensional Study in Elderly Humans

During elbow procedures, reconstruction of the joint (including the articular cartilage) is important in order to restore elbow function; however, the regional distribution of elbow cartilage is not completely understood. The purpose of the present study was to investigate the 3-dimensional (3-D) distribution patterns of cartilage thickness of elbow bones (including the distal part of the humerus, proximal part of the ulna, and radial head) in order to elucidate the morphological relationship among them.

Osteochondritis Dissecans of the Humeral Trochlea: Characterization of a Rare Disorder Based on 28 Cases

BACKGROUND

Osteochondritis dissecans (OCD) of the humeral trochlea is very rare. It may cause pain, mechanical symptoms, and loss of elbow motion, typically in the adolescent athlete. However, little published information is available regarding this condition.

PURPOSE

To describe the clinical presentation, radiographic features, and prognosis of trochlear OCD.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Over a 10-year period, 28 patients presented to a tertiary pediatric hospital with trochlear OCD. Medical records and imaging were analyzed to characterize presentation, lesions appearances, and outcomes.

RESULTS

Mean ± SD age at presentation was 13.4 ± 1.6 years, and 13 of the 28 patients were male. The most common presenting symptom was pain (93%), followed by crepitus (54%). Evidence of trochlear OCD could be seen on initial radiographs in 94% of cases but was commonly missed. Coexisting capitellar OCD lesions were the most common associated abnormalities seen on magnetic resonance imaging (21%). Investigators noted 2 predominant patterns: "typical" trochlear OCD lesions (89%) were located on the lateral crista of the trochlea, 3.1 ± 4.4 mm lateral to the apex of the trochlear groove. This location corresponded to the medial tip of the capitellar epiphyseal ossification center and was not actually on the trochlear ossification center. "Atypical" trochlear OCD lesions (11%) were located more posteromedially. Trochlear OCD lesions in 4 elbows were managed surgically, while the remainder were managed nonoperatively. At mean ± SD follow-up of 13 ± 8 months, 12 patients (43%) were asymptomatic. A further 5 patients had ongoing crepitus but no pain (18%), and 4 patients (14%) underwent surgical treatment for their trochlear OCD (osteochondral fixation, n = 1; drilling/curettage, n = 3); 3 of the 4 patients experienced some improvement in pain.

CONCLUSION

Although rare, trochlear OCD can cause considerable elbow problems. Clinicians should be aware of this differential diagnosis. Plain radiographs should be carefully scrutinized for subtle signs of trochlear OCD, particularly in the repetitive or overhead athlete with elbow pain. Although most patients' symptoms will improve with activity modification, some may require surgery.