Anteromedial Facet Research Articles

Role of 3D CT with Humeral Subtraction in Assessing Anteromedial Facet Coronoid Fractures

BackgroundThe anteromedial facet (AMF) of the coronoid is a key structure in resisting varus posteromedial rotatory instability (PMRI) of the elbow. However, not all isolated coronoid fractures involve the AMF and not all fractures involving the AMF are the result of a PMRI mechanism. There is debate regarding the management of isolated coronoid fractures. A reliable method of differentiating this heterogeneous group of isolated coronoid fractures is essential to develop an appropriate management algorithm. The aim of this study was to evaluate the role of additional humeral subtraction 3D images in the detailed assessment of the known radiographic features of AMF fractures with PMRI mechanism. MethodsThree upper extremity fellowship-trained orthopedic surgeons evaluated 32 consecutive CT scans in patients with isolated coronoid fractures, on two occasions separated by at least 5 months. On each occasion, CT scan images were evaluated for fracture morphology and orientation in two rounds. In the first round, the evaluation was made based on all 2D and 3D reconstruction images of the entire elbow; in the second round, the surgeons had access to images from the first round plus 3D reconstruction with humeral subtraction. Statistical analysis to assess agreement amongst the surgeons was performed using the kappa multi-rater analysis. Intraobserver agreement was evaluated using Pearson’s correlation coefficient. ResultsThe addition of the humeral subtraction view significantly improved the interobserver agreement for fracture morphology from 0.28 (95% CI 0.07-0.49) to 0.66 (95% CI 0.46-0.87), p< 0.001; and for orientation from 0.31 (95% CI 0.09-0.52) to 0.54 (95% CI 0.31-0.77), p<0.001. Similarly, the intraobserver Pearson correlation improved from 0.28-0.38 to 0.48-0.76 for fracture morphology, and from 0.36-0.77 to 0.51-0.69 for fracture orientation. Conclusion3D CT reconstruction with humeral subtraction improved surgeons’ ability to characterize radiographic features of AMF coronoid fractures. Future studies are required to determine whether better characterization of the morphology and orientation of AMF fractures allows for the categorization of these fractures into more homogenous groups and the development of more consistent management algorithms.

Coronoid fractures and complex elbow instability: current concepts.

Fractures of the coronoid process typically occur as part of more complex injury patterns, such as terrible triads, trans-olecranon fracture-dislocations, posteromedial rotatory injuries or Monteggia-like lesions. Each pattern is associated with a specific type of coronoid fracture with regard to shape and size and specific soft-tissue lesions. O' Driscoll classification incorporates those associations identifying three major types of fractures: tip, anteromedial facet, and basal fractures. The objective of this study is to review the most common types of complex elbow instability, identify the indications for coronoid fixation and guide the appropriate management. Tip fractures as those seen in terrible triads can conditionally left untreated provided that elbow stability has been restored after radial head fixation and ligaments repair. Anteromedial facet fractures benefit from a buttress plate, while large basilar fractures can be effectively secured with posteroanterior screws. Coronoid reconstruction with a graft should be considered in post-traumatic cases of chronic coronoid deficiency.

Does the coronoid fracture in terrible triad injury always need to be fixed?

BackgroundThe ideal treatment of terrble triad injuries and whether fixation of coronoid process fractures is needed or not are still debated. Therefore, we aimed to investigate if terrible triad injuries necessitate coronoid fracture fixation and evaluate if non-fixation treatments have similar efficacies and outcomes as fixation-treatments in cases of terrible triad injuries.MethodsFrom August 2011 to July 2020, 23 patients with acute terrible triad injuries without involvement of the anteromedial facet of the coronoid process were included to evaluate the postoperative clinical and radiological outcomes (minimum follow-up of 20 months). According to the preoperative height loss evaluation of the coronoid process and an intraoperative elbow stability test, seven patients underwent coronoid fracture fixation, and the other eight patients were treated conservatively. The elbow range of motion (ROM), Mayo Elbow Performance Score (MEPS), and modified Broberg-Morrey score were evaluated at the last follow-up. In addition, plain radiographs were reviewed to evaluate joint congruency, fracture union, heterotopic ossification, and the development of arthritic changes.ResultsAt the last follow-up, the mean arcs of flexion-extension and supination-pronation values were 118.2° and 146.8° in the fixation group and 122.5° and 151.3° in the non-fixation group, respectively. The mean MEPSs were 96.4 in the fixation group (excellent, nine cases; good, tow cases) and 96.7 in the non-fixation group (excellent, ten cases; good, two cases). The mean modified Broberg-Morrey scores were 94.0 in the fixation group (excellent, sevev cases; good, four cases) and 94.0 in the non-fixation group (excellent, ten cases; good, tow cases). No statistically significant differences in clinical scores and ROM were identified between the two groups. However, the non-fixation group showed a significantly lower height loss of the coronoid process than the fixation group (36.3% versus 54.5%).ConclusionsThere were no significant differences in clinical outcomes between the fixation and non-fixation groups in terrible triad injuries.

A novel fragment specific classification of complex olecranon fractures: 3-dimensional model design, radiological validation, and proposed surgical algorithm

BackgroundCurrent classifications for proximal ulna fracture patterns rely on qualitative data and cannot inform surgical planning. We propose a new classification system based on a biological and anatomical stress analysis. Our hypothesis is that fragment types in complex fractures can be predicted by the tendon and ligament attachments on the proximal ulna. MethodFirst, we completed a literature review to identify quantitative data on proximal ulna soft tissue attachments. On this basis, we created a 3D model of ulnar anatomy with SliceOMatic and Catia V5R20 software, and determined likely locations for fragments and fracture lines. The second part of the study was a retrospective radiological study. A level-one trauma radiological database was used to identify CT scans of multifragmentary olecranon fractures from 2009 to 2021. These were reviewed and classified according to the “fragment specific” classification and compared to the Mayo and the Schatzker classifications. ResultsTwelve articles (134 elbows) met the inclusion criteria and seven potential fracture fragments were identified. The radiological study included 67 preoperative CT scans (mean 55 years). The fragments identified were: Posterior (40%), intermediate (42%), tricipital (100%), supinator crest (25%), coronoid (18%), sublime tubercle (12%) and anteromedial facet (18%). Eighteen cases (27%) were classified as Schatzker D (comminutive) and 21 (31%) Mayo 2B (stable comminutive). Inter-rater correlation coefficient (ICC) was 0.71 among 3 observers. ConclusionThis proposed classification system is anatomically based and considers the deforming forces from ligaments and tendons. Having a more comprehensive understanding of complex proximal ulna fractures would lead to more accurate fracture evaluation and surgical planning.

A Medial Approach That Provides Ample Exposure of the Coronoid for Fracture Management.

We describe a medial approach to the coronoid where the flexor-pronator mass is released from its humeral origin by creating a proximally based tendinous flap. This technique facilitates access to the coronoid, preservation of the medial collateral ligament origin, and repair of the flexor-pronator mass. This approach has utility for all coronoid fracture variations but especially the O'Driscoll anteromedial subtype 3, which includes fractures of the sublime tubercle, the anteromedial facet, and the coronoid tip.

Outcomes and complications after treatment for anteromedial facet fracture of the coronoid process: A systematic review

BackgroundFracture of the anteromedial facet (AMF) of the coronoid process is associated with varus posteromedial rotatory instability (VPMRI). However, there is still controversy regarding the optimal treatment for AMF fracture. The purpose of this study is to report on a systematic review of the outcomes and complications after treatment for AMF fracture. MethodsThis study was conducted using electronic databases, PubMed, EMBASE and Scopus. Studies reporting outcome scores and complications were included. Studies that did not utilize O'Driscoll classification for AMF fractures were excluded. Through conduct of a thorough review of included studies, definite VPMRI were identified and cases involving other injury mechanisms were excluded. ResultsFifteen articles reporting on 246 patients were included. According to O'Driscoll classification, 6.2% of cases were anteromedial subtype I, 73.7% were subtype II, and 20.1% were subtype III. Two-hundred sixteen patients (87.8%) were treated surgically and 30 patients (12.2%) were treated conservatively. Lateral collateral ligament (LCL) injuries were 76.2% (157/206) and medial collateral ligament injuries were 16.9% (33/195). Among 216 cases who underwent surgical treatment, depending on the fragment size, displacement, and instability, coronoid fixation was performed in 189 cases and LCL repair alone was performed in 27 cases. The mean final Mayo Elbow Performance Score was 92.1 and the Broberg & Morrey score was 89.5. The overall complication and reoperation rates were 17.7% (41/232) and 12.9% (26/202). ConclusionsBoth surgical and conservative treatment for AMF fractures resulted in satisfactory final clinical outcomes. However, high complication and reoperation rates were observed.

Conservative versus surgical management of isolated O'Driscoll II coronoid fracture: A systematic review

PurposeThe purpose of this systematic review is to summarize the current literature on conservative and surgical management of isolated O'Driscoll II coronoid fracture. Study DesignSystematic review. MethodsWe systematically searched Medline, Embase, Google Scholar, and Web of Science databases for published studies by complying with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and using the keywords “isolated coronoid fracture,” “O'Driscoll type 2 coronoid fracture,” “anteromedial coronoid fracture,” “anteromedial facet coronoid fracture,” “posteromedial rotatory instability,” and “varus posteromedial rotatory instability.” Patients were divided into conservative treatment and surgical treatment groups. Oxford Centre for Evidence-Based Medicine and Methodological Index for Non-Randomized Studies were assessed to determine each article’s quality. The primary outcomes of the present reviews were the Mayo elbow performance score (MEPS) and the disabilities of the arm, shoulder, and hand (DASH) score, and the secondary outcomes were associated with complications and reoperations. Eligible trials were independently chosen by two review authors, and a third reviewer resolved all disagreements. ResultsThe search yielded 458 records, among which 446 articles were of relevance, and 12 were included. In the final review, 138 patients were evaluated—98 (71%) who received surgical treatment and 40 (29%) who received conservative treatment. The mean MEPS score and the DASH score of surgical treatment were 91 and 8, respectively; 69.8% of patients had excellent scores, and 27.0% had good scores. The mean MEPS score and the DASH score of conservative treatment were 92 and 12, respectively; 70.6% of patients had excellent scores, and 23.5% had good scores. ConclusionsIn select cases, conservative treatment can achieve good results in the treatment of isolated O'Driscoll II coronoid fracture when a stricter indication is followed. However, there is insufficient evidence to recommend the appropriate treatment for a particular fracture subtype, and there is a need for more high-quality randomized controlled trials to determine which treatment is superior.

Anteromedial coronoid facet fractures and associated ligament lesions: A case series

IntroductionVarus posteromedial rotational injury mechanisms lead to fractures of the coronoids process' anteromedial facet. As these fractures are often unstable, rapid fracture treatment is vital to prevent progressive osteoarthritis. Materials and methodsTwelve patients with a fracture of the anteromedial facet treated surgically were enrolled in the study. Computed tomography images were used to classify the fractures according to the system by O'Driscoll et al. Clinical follow-up included each patient's medical record, surgical treatment algorithm, all complications encountered during the follow-up period, Disabilities of the arm, shoulder, and hand score, subjective elbow value, and pain. ResultsA total of 8 men (66.7%) and 4 women (33.3%) were treated surgically and followed-up after a mean period of 45 ± 23 months. The mean DASH score was 11.9 ± 12.9 points. One patient complained of transient neuropathy in the innervation area of the ulnar nerve, however, this existed already pre-operatively and resolved after less than three months. ConclusionsThe presented patient cohort shows that AMF fracture of the coronoid process are unstable lesions according to the bony instability and the frequently ruptured collateral ligament complexes which need to be addressed. The MCL seems to be affected more frequently than previously appreciated. Level of evidenceLevel IV; Case Series; Treatment Study.

Coronoid Fractures and Varus Posteromedial Rotatory Instability

Coronoid fractures are associated with elbow fracture-dislocations. Fractures involving the anteromedial facet of the coronoid often are associated with a posteromedial rotational instability pattern which requires careful management to avoid persistent and often subtle instability. Although some anteromedial coronoid fractures may be treated nonoperatively, internal fixation through a medial approach is indicated in most cases. Without a universally accepted treatment algorithm, surgeons should consider the risk of persistent instability when approaching this injury pattern. Fracture morphology, fragment size, and joint congruity, as determined by CT imaging and physical examination, inform clinical decision making.

Medial Elbow Exposure: Modified Taylor-Scham Versus Flexor Carpi Ulnaris-Split.

To compare the exposure of the coronoid process, anteromedial facet, and anterior band of the medial collateral ligament using the flexor carpi ulnaris (FCU)-splitting approach with the Taylor-Scham approach modified with an ulnar nerve transposition. Thirty approaches were performed on 15 fresh cadavers using a randomized cross-over design and standardized incision. Access to key anatomic landmarks was assessed, and a calibrated digital image was taken from the surgeon's best perspective of each approach. Images were analyzed using ImageJ (National Institutes of Health) software to calculate the area of osseous exposure. All key anatomic landmarks were visualized using both approaches. The average area of exposure for the Taylor-Scham was 19.5 cm 2 compared with 13.6 cm 2 for the FCU-splitting ( P < 0.0001). The distal extent of the FCU-splitting approach is limited by the ulnar nerve and its branches to the humeral head of the FCU. The Taylor-Scham approach provides a more extensile exposure of the anteromedial coronoid and proximal ulna than the FCU-splitting approach while avoiding cross-tensioning of the ulnar nerve.

The simulation of terrible triad injuries in fresh-frozen human cadaveric specimens with intact soft tissue envelope

IntroductionThe aim of the present study was to develop a technical process to reproducibly generate terrible triad injuries (TTI) in fresh-frozen human cadaveric specimens, while leaving the skin intact. Such “pre-fractured” specimens, used for scientific analysis and for surgical education, might help to improve current treatment, which is complex and prone to complications.Materials and methodsTo induce the desired fractures, a custom-made fracturing unit was used to apply an axial force on the extended cadaveric elbow specimens, with the forearm pronated and under valgus load. To simulate the valgus load, a pneumatic cylinder was developed to apply valgus stress to the joint by an additional force vector from the lateral side of the joint.ResultsThe success rate of TTI induction was 92.3% (12/13). Of the 12 radial head fractures, 3 (25%) were classified Mason type II and 9 (75%) Mason type III. The coronoid fractures were grouped in tip subtype 2 (5 fractures, 41.7%), anteromedial facet (AMF) subtype 2 (4 fractures, 33.3%), AMF subtype 3 (1 fracture, 8.3%) and basal subtype 1 (2 fractures, 16.7%).ConclusionsThe present study provides an instrument for successful and reproducible production of dislocation fracture patterns with their typical accompanying soft tissue lesions. The methodology might be applied on a broad basis to be able to perform biomechanical studies regarding primary stability of fixation concepts for TTI and to educate surgeons in a fairly realistic scenario with the surgical treatment of TTI.

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

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. 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. Measurements showed a mean coronoid height of 15mm, which was 42% of ulnar height with gender-specific differences (mean 16mm in men and 14mm in women, P < 0.001). A mean unsupported anteromedial facet width of 8mm 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 52mm distal to olecranon tip. The average proximal ulna varus angulation was 16° at a mean of 74mm 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. 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.

Optimal K-Wire Placement for Indirect Cannulated Screw Fixation of Coronoid Process Fractures: A Radiology-Based Guide

Indirect fixation of coronoid process fractures of the ulna, especially arthroscopically, offers the possibility to avoid extensive medial surgical approaches. However, optimal placement of K-wires for cannulated screw fixation is technically challenging. The aim of the present study was to present guide values for K-wire placement for indirect screw fixation of coronoid tip (COT) and anteromedial facet (AMF) fractures of the ulna. Computed tomography scans of the elbows of 197 patients with an uninjured ulna were identified and evaluated following a standard measuring protocol. Optimal placement of K-wires was defined as the bisector between the anterior and articular cortex while respecting a 1.6-mm safe zone for each placement. This placement of the K-wires in the COT and the AMF was analyzed by measuring the wire angulation in relation to the posterior ulnar cortex (AUC), the distance from the entry point to the posterior olecranon edge (DPE), and the intraosseous length (IOL). Because the coronoid has a curved shape, measurements of the COT and AMF were expected to differ significantly. Sex was also expected to influence measurements. To determine whether this optimal placement of K-wires can be reliably identified, interobserver and intraobserver reliabilities were evaluated. To address tip fragments, we determined a mean AUC of 64°, DPE of 36 mm, and IOL of 38 mm. Regarding wire placement toward the AMF, the means for the AUC, DPE, and IOL were 79°, 27 mm, and 33 mm, respectively. Statistically significant differences were found between the COT and the AMF for the AUC, DPE, and IOL. Our measuring protocol showed good interobserver and intraobserver reliability. K-wire placement toward the COT demands a smaller angle, a longer IOL, and a more distal entry point than wires placed toward AMF. These differences reflect the curved and complex anatomy of the coronoid. This measuring algorithm can be used to plan osteosynthesis, and the obtained reference values can help understand the coronoid's complex anatomy.

The loads developed by epicondylar and epitrochlear muscles across the elbow joint. A dynamic simulated model

The radio-humeral joint has traditionally been believed to support most of the loads transmitted through the elbow. Load transfer through the elbow has been a controversial issue since the publication of the first biomechanical studies on the subject, most of which were based on extrinsic forces acting on the extended joint. The present study analyzes load distribution across the six different compartments in the elbow while the joint is flexed, as well as the intrinsic forces generated in the epicondylar and epitrochlear muscles.Ten cadaveric elbows were positioned at 90° of flexion, forearm in a neutral position and wrist at 0°. Tekscan sensors were used for measuring intraarticular pressures.Forces generated by epitrochlear muscles results in a series of loads that affect mainly the anteromedial facet (40%), followed by the posterolateral facet (34%) of the ulnohumeral joint, with the flexor carpi ulnaris generating the heaviest loads (43% on the anteromedial and 38% on the posterolateral facets). Conversely, the forces generated by the epicondylar muscles, similar in behavior but with an opposite direction, convey heavier loads to the elbow’s anterolateral facet (45%), followed by the radiohumeral joint (26%) with the extensor carpi ulnaris generating the heaviest loads (54% on the anterolateral facet and 17% on the radiohumeral joint).Our results indicate that the elbow joint exhibits a characteristic load distribution pattern that depends on the muscles, as intrinsic forces are generated by the epicondylar and epitrochlear muscles. The anterior portion of the ulnohumeral joint is the area bearing the heaviest loads.

Coronoid reconstruction with autologous iliac crest bone graft in chronic elbow instability through amedial approach

Neutralizing a posteromedial rotatory instability (PMRI) caused by coronoid deficiency by restoration of the humeroulnar joint surface with an autologous iliac crest bone graft. Surgery is indicated in patients with chronic deficiency of the anteromedial facet of the coronoid with subsequent PMRI. Coronoid reconstruction is not recommended in patients with advanced osteoarthritis of the elbow caused by subluxation of the humeroulnar joint. General contraindications like acute infection, pregnancy and lack of operability should also be taken into account. First, amedial approach is established and the base of the coronoid is prepared. Afterwards an autologous iliac crest bone graft is placed onto the defect and secured by screws or aplate. In addition, a reconstruction of the anterior bundle of the medial collateral ligament with an autologous tendon graft is performed. An elbow orthesis is worn for 6weeks after surgery to avoid valgus or varus stress. There is no restriction in range of motion. Acontinuous passive motion elbow chair supports the patient in regaining elbow mobility. Between 2015 and 2017, we treated 10patients suffering from chronic coronoid defects with coronoid reconstruction. Eight of the patients were available for follow-up 86weeks after surgery. The mean age was 41.4years. In all patients, elbow range of motion and patient-related outcome measures were improved after surgery. Plain radiographs illustrated correct centering of the elbow joint. One patient had to undergo elbow arthroplasty and was excluded. Coronoid reconstruction with an autologous iliac crest bone graft restored humeroulnar joint congruency and improved satisfaction in patients suffering from chronic coronoid deficiency.

Classification of coronoid process fractures: A pending question.

Ulna coronoid fracture is a complicated elbow injury. Comprehensive classification of coronoid fracture can assist diagnosis, guide treatment, and improve prognosis. Existing coronoid fracture classifications are insufficient to interpret all fracture patterns. The coronoid fracture classification is associated with elbow-specific trauma patterns. Coronoid fractures are often associated with other elbow injuries, commonly with radial head fractures, which makes the clinical strategies inconsistent and prognosis poor. The current fracture classifications do not contain information about combined injuries. Preservation of ulnohumeral joint contact after trauma is critical to elbow mechanical and kinematic stability. Important fracture types for treatment include terrible-triad injuries and anteromedial facet fractures. Open reduction and internal fixation of these two fractures should be conducted when marked displacement of the fragment, elbow instability under stress, and complicated associated injuries. The current surgical tactics based on classifications are still controversial.

Operative Fixation of the Anteromedial Facet of the Coronoid Process.

Anteromedial coronoid facet fractures typically occur with varus, pronation, and axial forces applied to the elbow. Due in part to the high rate of concomitant lateral collateral ligament (LCL) injuries, untreated anteromedial facet fractures can result in varus and posteromedial rotatory elbow instability. Although small fractures that are not amenable to open reduction and internal fixation can be treated with isolated LCL repair, larger fragments are treated with buttress plating on the anteromedial surface of the coronoid with or without LCL repair. The "over-the-top" approach via a split in the flexor pronator mass is the preferred method of accessing the anteromedial facet. Although data regarding the functional outcomes after operative fixation of the anteromedial facet are limited, observational studies have demonstrated good restoration of elbow stability and motion.

The radiological findings in complex elbow fracture-dislocation injuries.

Elbow fracture-dislocation is a complex injury which can lead to significant bony and soft tissue damage. Surgical intervention is guided towards restoring joint stability, allowing early mobilization and preventing long-term joint stiffness. The most common types are posterolateral, posteromedial, Monteggia type (and variants), and anterior trans-olecranon fracture-dislocations. Posterolateral fracture-dislocation is characterized by a radial head fracture (± anterolateral coronoid fracture) and typically capsuloligamentous disruption (lateral collateral ligaments injury is the most common). A posterolateral fracture-dislocation with radial head and coronoid anterolateral facet fractures is termed a terrible triad injury. In posteromedial fracture-dislocation, there is a fracture of the anteromedial facet of the coronoid, typically with proximal avulsion of the lateral collateral ligaments (± injury to the posterior bundle of the ulnar collateral ligament). Monteggia fracture-dislocation injuries demonstrate proximal ulnar fracture (with possible involvement of the olecranon and the coronoid) and radial head dislocation. These can be divided into apex anterior or apex posterior variants. The latter are commonly associated with radial head fractures and lateral ligamentous injury, and have a worse prognosis. In trans-olecranon fracture-dislocation, there is significant disruption of the greater sigmoid notch and the olecranon, with various involvement of the coronoid and the proximal ulna. The article describes the radiological findings and outlines the management principles in complex elbow fracture-dislocation injuries.

Clinical comparison of the over-the-top and flexor carpi ulnaris split approaches for the treatment of anteromedial facet fracture of the coronoid process.

The flexor carpi ulnaris (FCU)-split approach and the over-the-top approach have been used frequently for the fixation of anteromedial facet (AMF) fractures of the coronoid process. Clinical studies have not compared functional recovery and complication rates associated with these approaches. This study aimed to compare the clinical effectiveness of the over-the-top and FCU-split approaches for the treatment of AMF fractures of the coronoid process. Thirty-two patients who underwent surgery for AMF fractures between January 2013 and August 2019 were divided into the FCU-split and over-the-top groups. The FCU-split approach was used from January 2013 to March 2016, and the over-the-top approach was used from April 2016 to August 2019. Bony union, radiographic signs of osteoarthritis (Broberg and Morrey classification), and development of heterotopic ossification were evaluated. Postoperative pain score (visual analog scale at 2 days after the operation), surgical time (minutes), range of motion of the elbow, elbow function (Mayo Elbow Performance Score [MEPS]), and the presence of postoperative ulnar neuropathy were also compared between the 2 groups. The FCU-split and over-the-top approaches were performed in 15 and 17 patients, respectively. The mean age was 46 ± 13 years (range, 22-67 years), and the mean follow-up duration was 19± 6.7 months (range, 13-38 months). All coronoid fractures had a solid osseous union during the follow-up, and no subluxation or dislocation was observed in the 2 groups. The occurrence of heterotopic ossification and the grade of post-traumatic arthritis did not differ significantly between the groups (all P > .05). There were also no significant differences between the groups in terms of postoperative pain score, range of motion, and MEPS (all P > .05). However, the surgical time was shorter for the over-the-top approach than that for the FCU-split approach (79± 23 vs. 101 ± 14, P = .008), and the surgical time was significantly associated with the fracture classification and surgical approach (P = .001 and .003, respectively). In addition, postoperative ulnar neuropathy occurred less with the over-the-top approach than with the FCU-spilt approach (5.9% vs. 46%, P = .013). Both the FCU-split and over-the-top approaches were appropriate for performing the buttress plate fixation for AMF fractures of the coronoid process and for restoring the elbow stability. The fixation of AMF fractures through the over-the-top approach was technically easier and had less incidence of postoperative ulnar neuropathy.

Three-dimensional cortical and trabecular bone microstructure of the proximal ulna.

The three-dimensional (3D) microstructure of the cortical and trabecular bone of the proximal ulna has not yet been described by means of high-resolution 3D imaging. An improved characterization can provide a better understanding of their relative contribution to resist impact load. The aim of this study is to describe the proximal ulna bone microstructure using micro-computed tomography (micro-CT) and relate it to gross morphology and function. Five dry cadaveric human ulnae were scanned by micro-CT (17μm/voxel, isotropic). Both qualitative and quantitative assessments were performed on sagittal image stacks. The cortical thickness of the trochlear notch and the trabecular bone microstructure were measured in the olecranon, bare area and coronoid. Groups of trabecular struts starting in the bare area, spanning towards the anterior and posterior side of the proximal ulna, were observed; within the coronoid, the trabeculae were orthogonal to the joint surface. Consistently among the ulnae, the coronoid showed the highest cortical thickness (1.66 ± 0.59mm, p = 0.04) and the olecranon the lowest (0.33 ± 0.06mm, p = 0.04). The bare area exhibited the highest bone volume fraction (BV/TV = 43.7 ± 22.4%), trabecular thickness (Tb.Th = 0.40 ± 0.09mm) and lowest structure model index (SMI = -0.28 ± 2.20, indicating plate-like structure), compared to the other regions (p = 0.04). Our microstructural results suggest that the bare area is the region where most of the loading of the proximal ulna is concentrated, whereas the coronoid, together with its anteromedial facet, is the most important bony stabilizer of the elbow joint. Studying the proximal ulna bone microstructure helps understanding its possible everyday mechanical loading conditions and potential fractures. N.A.