Reproducibility of the Mayo and Schatzker classification systems in proximal ulna fractures

INTRODUCTION

A fracture classification system should provide a reliable and reproducible means of communication between different parties. It should be logical and understandable, with few categories to memorize. The aim of this study was to determine the intra- and interobserver reliability of the Schatzker and Mayo classification systems for the assessment of proximal ulna fractures.

MATERIALS AND METHODS

Intra- and interobserver reliability studies were conducted on 39 X-rays of injured elbows drawn randomly from 74 cases previously used in a series on predictors of ulnohumeral osteoarthritis in proximal ulna fractures. Ten observers independently reviewed these X-rays on 2 separate occasions 3 months apart. The fracture type was assessed according to the Schatzker and Mayo classification systems during each reading session. Cohen's and Fleiss' kappa were used to measure the intra- and interobserver reliability.

RESULTS

The Schatzker classification had a fair interobserver reliability for the first (Schatzker R1, Fleiss' κ: 0.394) and second (Schatzker R2, Fleiss' κ: 0.351) readings. The mean intraobserver reliability value between the 10 reviewers for the Schatzker classification was rated as substantial (0.61). The Mayo classification had a fair interobserver reliability for the first (Mayo R1, Fleiss' κ: 0.278) and second (Mayo R2, Fleiss' κ: 0.292) readings. The mean intraobserver reliability value between the 10 reviewers for the Mayo classification was rated as fair (0.52).

DISCUSSION

The classification systems for proximal ulna fractures showed poor reproducibility between the different observers since they had low interobserver agreement values. Nevertheless, their use remained reliable since the measured intraobserver agreement value was deemed substantial.

LEVEL OF EVIDENCE

IV; retrospective.

Reliability of the CURL classification for proximal ulna fracture-dislocations of the elbow

Background

Proximal ulna fracture-dislocations are challenging injuries with a myriad of existing classification systems. The Coronoid, proximal Ulna, Radius, and Ligaments classification (CURL) is a simple framework designed to focus attention on the key components affecting outcome and guide surgical management. This study evaluates interobserver and intraobserver reliability of this new classification.

Methods

Four observers independently reviewed plain radiographs and computed tomography (CT) scans of patients with proximal ulna fracture-dislocations. Each observer scored the Coronoid (C), proximal Ulna (U), and Radius (R) components for each fracture on 2 occasions. The osseous components were subclassified as 'intact', 'simple', or 'complex'. The Ligament component (L) was not rated as this requires intraoperative classification. Interobserver and intraobserver reliability was calculated using Cohen's weighted kappa coefficients. X-ray and CT were compared for patients with both imaging modalities. The Landis and Koch criteria were used to interpret the strength of the kappa statistics.

Results

One hundred seventy seven patients had plain X-rays; 58 patients had both X-ray and CT scans. Overall, in the X-ray only cohort, there was 'almost perfect' interobserver reliability for the radial head (k = 0.94) and coronoid (k = 0.83), and 'substantial' reliability (k = 0.68) for the proximal ulna. For the X-ray and CT cohort, interobserver reliability was 'almost perfect' across both modalities for the radial head (k = 0.88 and k = 0.93, respectively) and 'moderate' for the proximal ulna (k = 0.48 and k = 0.52, respectively). For the coronoid, interobserver reliability for X-ray interpretation was 'substantial' (k = 0.74) and for CT was 'almost perfect' (k = 0.89). Intraobserver reliability was 'almost perfect' for all components, other than CT assessment of the proximal ulna which demonstrated 'substantial' reliability (k = 0.74).

Conclusion

The Coronoid, proximal Ulna, Radius, and Ligaments classification demonstrates strong interobserver and intraobserver reliability, supporting use of the classification for proximal ulna fracture-dislocations. CT is recommended for improved characterization of any fracture with a coronoid component.

The role of surgery in the treatment of neuroblastoma metastases at rare sites

PURPOSE

Treatment of neuroblastoma metastases usually consists of chemotherapy and irradiation. However, in selected cases, surgical treatment is also indicated. In this study, we present three cases of patients with neuroblastoma metastases at rare sites that underwent surgery.

MATERIALS AND METHODS

We retrospectively analyzed data of patients who underwent surgery for neuroblastoma at our department of Pediatric Surgery and Pediatric Urology at the University Children's Hospital in Tuebingen and selected those patients who had surgery explicitly for a metastasis.

RESULTS

Between 2002 and 2020, 277 children underwent surgical treatment for neuroblastoma. Three cases with metastases at exceptional sites are presented here after therapy according to protocols. One patient had a penile metastasis and received surgery including a plastic reconstruction. The patient showed no signs of erectile or urinary dysfunction at follow-up. Another patient had a metastasis in the proximal ulna, which remained vital even after exhausted treatment after two relapses. Afterward there was no restriction of movement of the extremity. The third patient had, amongst others, metastases to the pancreatic body and to the liver. Both were surgically removed during primary tumor resection. This patient died after local tumor relapse. The other two patients showed no evidence of tumor relapse after a follow-up of 18 and 17 months, respectively.

CONCLUSION

Although children with neuroblastoma often present with metastases, there is no recommendation for surgical treatment other than diagnostic biopsies. In case of persistence of metastasis or after exhaustion of high-risk therapy, surgical resection must be considered.

[Monteggia-like injuries : Pitfalls of surgical treatment]

The term Monteggia-like lesions or Monteggia equivalent injuries includes fractures of the proximal ulna with dislocation and dislocation fractures of the radial head from the proximal radio-ulnar joint. The complexity of the injury requires a dedicated understanding of the anatomical structures and their biomechanical properties. Particularly due to the rarity, the complication and revision rates are high. A conservative treatment is not usually effective. Three-dimensional imaging by computed tomography is part of the surgical preparation. The goal of surgical treatment is osteosynthetic reconstruction of the fractures and restoration of joint congruency. In cases of nonreconstructable radial head fractures, radial head arthroplasty may be necessary. In addition to reconstruction of the bony stabilizers, refixation of the ligamentous structures is essential for treatment success. The combination of complex fracture patterns and possible dislocation positions in the ulnohumeral, radiohumeral and proximal radio-ulnar joints poses a great challenge to the surgeon. The most frequent complications are peri-implant infections, implant failure, loss of reduction, stiffness or instability. Especially the anatomical configuration of the proximal ulna is complex and requires accurate reconstruction. Therefore, reconstruction of the proximal ulna in length and rotation, including the coronoid process, is considered to be a key factor in the surgical treatment of Monteggia-like injuries.

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.

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

INTRODUCTION

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.

MATERIALS AND METHODS

Five dry cadaveric human ulnae were scanned by micro-CT (17 μm/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.

RESULTS

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 ± 0.59 mm, p = 0.04) and the olecranon the lowest (0.33 ± 0.06 mm, p = 0.04). The bare area exhibited the highest bone volume fraction (BV/TV = 43.7 ± 22.4%), trabecular thickness (Tb.Th = 0.40 ± 0.09 mm) and lowest structure model index (SMI = - 0.28 ± 2.20, indicating plate-like structure), compared to the other regions (p = 0.04).

CONCLUSIONS

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.

LEVEL OF EVIDENCE

N.A.

Proximal ulna non-union: treatment concept and postoperative outcome

PURPOSE

Non-union of the proximal ulna is a serious complication after surgical treatment of olecranon and complex elbow fractures, frequently leading to poor functional outcome. To date, there is a lack of data regarding optimal treatment strategies and functional outcome parameters after surgical revision.

METHODS

From 02/2010 to 12/2018, 31 patients undergoing surgical treatment of proximal ulna non-union could be included. Follow-up period was seven years (SD 2.5 years). All patients were clinically assessed using a clinical assessment tool set and standard elbow scores (MEPS, OES, DASH score). All complications and unplanned revision surgeries were recorded and all radiographic material was analyzed.

RESULTS

Initial non-union procedures were performed at an average of 6.6 months (SD 3 months) after the index procedures. Those included the use of autologous spongiosa graft in all patients and concomitant compression re-osteosynthesis in 28 patients. Radiological consolidation was achieved in all patients. Overall, patients achieved a good to fair functional outcome with Mayo elbow performance score measuring 78.5 (SD 9.1), DASH score 34.7 (SD 14.4), and Oxford elbow score 31.2 (SD 6.6) points. Initial malreduction/implant-malposition could be identified as a main reason for the occurrence of the non-union. Furthermore, inferior postoperative outcome was detected in patients > 60 years and BMI > 30 kg/m².

CONCLUSION

Using a standardized protocol, bony union and acceptable functional outcomes can be achieved in proximal ulna non-unions. However, surgeons should be aware of potential risk factors and proper initial fracture reduction as key to achieve sufficient bone healing.

Elbow hemiarthroplasty with a 3D-printed megaprosthesis for defects of the distal humerus or proximal ulna after tumour resection : a preliminary report

AIMS

The aim of this study was to investigate the feasibility of application of a 3D-printed megaprosthesis with hemiarthroplasty design for defects of the distal humerus or proximal ulna following tumour resection.

METHODS

From June 2018 to January 2020, 13 patients with aggressive or malignant tumours involving the distal humerus (n = 8) or proximal ulna (n = 5) were treated by en bloc resection and reconstruction with a 3D-printed megaprosthesis with hemiarthroplasty, designed in our centre. In this paper, we summarize the baseline and operative data, oncological outcome, complication profiles, and functional status of these patients.

RESULTS

Preparation of the prosthesis was a mean of 8.0 days (SD 1.5), during which time no patients experienced tumour progression. The mean operating time and intraoperative blood loss were 158.1 minutes (SD 67.6) and 176.9 ml (SD 187.8), respectively. All of the prostheses were implanted successfully. During a mean follow-up of 25.7 months (SD 7.8), no patients died, but four had complications (two superficial wound problems, one temporary palsy of radial nerve, and one dislocation). No aseptic loosening, structural failure, infection, heterotopic ossification, or degenerative arthritis was seen in this study. The mean flexion of the elbow was 119.6° (SD 15.9°) and the mean extension lag was 11.9° (SD 13.8°). The mean Musculoskeletal Tumor Society 93 score and Mayo Elbow Performance Score were 28.4 (SD 0.9) and 97.7 (SD 4.4), respectively.

CONCLUSION

The custom-made, 3D-printed megaprosthesis with hemiarthroplasty is a feasible option for functional reconstruction after resection of a tumour in the distal humerus or proximal ulna. Cite this article: Bone Joint J 2022;104-B(6):747-757.

The pediatric proximal ulna: a radiographic study

INTRODUCTION

The proximal ulna has been comprehensively described in the anatomic literature and imaging studies. However, to the best of our knowledge, the anatomy of the proximal ulna in children has not been fully described in the literature.

METHODS

The present study was conducted on 189 children aged between 0 and 12 years (4.7 ± 2.7) by analysis of lateral X-rays of the forearm. Proximal ulna dorsal angulation (PUDA), tip-to-apex (TTA), and total ulnar length (TUL) were measured. The correlation between age and the various X-ray measurements was recorded and then compared with gender differences and adult measurements. Three orthopedic surgeons independently examined the X-ray films and confirmed the reliability of the original observations through intra-group correlation coefficients.

RESULTS

There was a strong positive correlation between age and TUL (r = 0.834), and a moderately negative correlation between age and PUDA (r = - 0.405). No significant differences were observed between different genders (p > 0.05). Compared with adults, all measurements were smaller except for PUDA, all such measurements statistically significantly different between children and adults (p < 0.05). Interobserver and intraobserver reliability were "very good" for TUL (0.81-1.00), and "good" for PUDA, TTA, and TTA% (0.61-0.80).

CONCLUSIONS

Good understanding of the anatomy of the pediatric proximal ulna will help to increase the knowledge base in pediatric orthopedic surgeons allowing them to provide improved treatment of fractures. Restoration of the correct forearm anatomy should result in superior clinical and functional results.

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.

Novel Radiographic Indexes for Elbow Stability Assessment: Part B-Preliminary Clinical Study

INTRODUCTION

The coronoid process plays a key-role in preserving elbow stability. Currently, there are no radiographic indexes conceived to assess the intrinsic elbow stability and the joint congruency. The aim of this study is to present new radiological parameters, which will help assess the intrinsic stability of the ulnohumeral joint and to define normal values of these indexes in a normal, healthy population.

METHODS

Four independent observers (two orthopaedic surgeons and two radiologists) selected lateral view X-rays of subjects with no history of upper limb disease or surgery. The following radiographic indexes were defined: trochlear depth index (TDI); anterior coverage index (ACI); posterior coverage index (PCI); olecranon-coronoid angle (OCA); radiographic coverage angle (RCA). Inter-observer and intra-observer reproducibility were assessed for each index.

RESULTS

126 subjects were included. Standardized lateral elbow radiographs (62 left and 64 right elbows) were obtained and analysed. The mean TDI was 0.46 ± 0.06 (0.3-1.6), the mean ACI was 2.0 ± 0.2 (1.6-3.1) and the mean PCI was 1.3 ± 0.1 (1.0-1.9). The mean RCA was 179.6 ± 8.3° (normalized RCA: 49.9 ± 2.3%) and the mean OCA was 24.6 ± 3.7°. The indexes had a high-grade of inter-observer and intra-observer reliability for each of the four observers. Significantly higher values were found for males for TDI, ACI, PCI and RCA.

CONCLUSION

The novel radiological parameters described are simple, reliable and easily reproducible. These features make them a promising tool for radiographic evaluation both for orthopaedic surgeons and for radiologists in the emergency department setting or during outpatient services.

LEVEL OF EVIDENCE

Basic Science Study (Case Series).

CLINICAL RELEVANCE

The novel radiological parameters described are reliable, easily reproducible and become handy for orthopaedic surgeons as well as radiologists in daily clinical practice.

Nailing vs. plating in comminuted proximal ulna fractures - a biomechanical analysis

Background

Comminuted proximal ulna fractures are severe injuries with a high degree of instability. These injuries require surgical treatment, usually angular stable plating or double plating is performed. Nailing of proximal ulna fracture is described but not performed regularly. The aim of this study was to compare a newly developed, locked proximal ulna nail with an angular stable plate in an unstable fracture of the proximal ulna. We hypothesize, that locked nailing of the proximal ulna will provide non-inferior stability compared to locked plating.

Methods

A defect fracture distal to the coronoid was simulated in 20 sawbones. After nailing or plate osteosynthesis the constructs were tested in a servo-pneumatic testing machine under physiological joint motion (0°-90°) and cyclic loading (30 N – 300 N). Intercyclic osteotomy gap motion and plastic deformation of the constructs were analyzed using micromotion video-analysis.

Results

The locked nail showed lower osteotomy gap motion (0.50 ± 0.15 mm) compared to the angular stable plate (1.57 ± 0.37 mm, p < 0.001). At the anterior cortex the plastic deformation of the constructs was significantly lower for the locked nail (0.09 ± 0.17 mm vs. 0.39 ± 0.27 mm, p = 0.003). No statistically significant differences were observed at the posterior cortex for both parameters.

Conclusions

Nail osteosynthesis in comminuted proximal ulna fractures shows lower osteotomy gap motion and lower amount of plastic deformation compared to locking plate osteosynthesis under laboratory conditions.

Anatomically shaped locking plates for radial head and olecranon fracture fixation in Monteggia-like lesions

BACKGROUND

Monteggia-like lesions are rare injuries. We retrospectively reviewed 40 consecutive patients with Monteggia-like lesions treated at a level I trauma center from 2009 to 2016. Clinical results were evaluated with a focus on the use of modern locking plates.

OBJECTIVE AND METHODS

Twenty-eight patients had Bado type II fractures, 11 had Bado type I, and 1 had Bado type III. All patients were treated by plate fixation of the ulna with a locking compression plate or double mini-plates. Fixation or replacement was performed for radial head fractures. We characterized all fractures and recorded the range of motion (ROM); 100-point visual analog scale (VAS) scores for pain and function; Disabilities of the Arm, Shoulder and Hand (DASH) score; and Mayo Elbow Performance Score (MEPS). A follow-up rate of 78% was reached at an average of 36 months (range, 12-95 months).

RESULTS

Stable fixation without recurrent instability was accomplished. The average ROM for flexion reached 130∘ with an extension deficit of 13∘. The sum of supination and pronation was 136∘. The VAS scores for pain and function were 20 and 75, respectively. The average MEPS and DASH scores were 84 and 28, respectively. Bado type I fractures had better outcomes for all variables, especially forearm rotation (p< 0.05). The complication rate was 22.5% and revision rate was 17.5%.

CONCLUSION

This fracture repair technique can safely achieve good and excellent outcomes in most cases and is partly superior to previously published techniques. However, Bado type II fractures still have a risk of poor results.

Ulnar trochlear notch articular surface has three morphological patterns: a neglected major anatomical feature

PURPOSE

The typical anatomical illustration of the trochlear notch articular surface includes a transverse rough non-articular ridge which separates the olecranon and coronoid part of the joint. This transverse ridge, the "bare area", is not covered by cartilage and represents the optimal entry point for olecranon osteotomies. Aim of the present study was to encounter the anatomical variations in the morphology of the trochlear notch articular surface.

METHODS

Two-hundred seventy-three dried ulnae were inspected and a qualitative classification of the variations of the trochlear notch articular surface was done. Correlation to gender and side was examined.

RESULTS

Three distinct morphological patterns were observed. Separate olecranon and coronoid facets (Type I) were the most common pattern (165/273, 60.4%). Partial fusion of olecranon and coronoid facets (Type II) was observed in 75 out of 273 bones (27.5%), while a single olecranon and coronoid facet (Type III) was present in 33 out of 273 bones (12.1%). The occurrence of Type II and III was significantly more common in females (p < 0.001).

CONCLUSIONS

The most common morphological pattern of the proximal ulna articular surface was the olecranon and coronoid facets separated by the transverse ridge, which is considered as the typical anatomical pattern. The partial fusion of olecranon and coronoid facets was the second most common pattern (27.5%) and the single olecranon and coronoid facet with no transverse ridge present was the rarest one (12.1%). These variations affect the area covered by cartilage. They are noticeable in an elbow MRI and they may have implications on olecranon osteotomy. Absence of the transverse ridge may confuse the surgeon during elbow arthroscopy.

Plate Osteosynthesis of Proximal Ulna Fractures-A Biomechanical Micromotion Analysis

PURPOSE

Double plating has been promoted, in recent years, as an alternative treatment method for proximal ulna fractures. This study aimed to compare the biomechanical properties of double-plate osteosynthesis with posterior plate fixation using a novel investigational design utilizing a 3-dimensional camera system to analyze fracture micromotion.

METHODS

Fourteen fresh-frozen specimens were available for this study. Mayo type IIA fractures of the olecranon were created and internal fixation was performed with either an angular stable posterior plate or angular stable double plates. Fracture micromotion was evaluated by means of digital image correlation with a 3-dimensional camera system before and after dynamic cyclic loading from 15° to 90° of elbow flexion with a pulling force of 25 N to 80 N.

RESULTS

Micromotion of fragments was less pronounced in double-plate osteosynthesis when compared with single plates before and after cyclic loading. However, overall results were similar. Two of the single plates failed during cyclic loading but there were no failures in the double plates.

CONCLUSIONS

This biomechanical analysis shows that single and double plating results in comparable stability of fixation. Although the double-plating technique tends to provide more stable fixation, relevant differences were not observed.

CLINICAL RELEVANCE

Double plating potentially represents an efficient option for fixation of proximal ulna fractures. It could decrease the risk of soft tissue complications owing to their low profile and the superior soft tissue coverage.

The Bare Area of the Proximal Ulna: An Anatomic Study With Relevance to Chevron Osteotomy

PURPOSE

A chevron osteotomy of the ulna is widely used to obtain intra-articular access to the elbow in the treatment of type C distal humerus fractures. The trochlear notch of the proximal ulna is divided into 2 articular parts by the "bare area." Ideally, the olecranon osteotomy should be centered on the bare area to minimize damage to the joint cartilage. The goals of this study were to describe the anatomy of the bare area and design an ideal chevron-shaped osteotomy.

METHODS

We dissected 38 cadaver elbows and measured the width of the bare area, the distance between the tip of the triceps insertion and the area on the olecranon cortex corresponding to the bare area. We then designed a chevron osteotomy to stay within the bare area and measured the distance from the tip of the triceps insertion to the osteotomy apex as well as the angle of the osteotomy plane and the angle of the chevron cuts.

RESULTS

The bare area existed in all 38 cadavers. The mean longitudinal and transverse widths were 4.0 mm (range, 1.0-8.6 mm) and 19.0 mm (range, 16.9-23.8 mm), respectively. The mean distance between the tip of the triceps insertion and the area on the olecranon cortex corresponding to the bare area was 19.0 mm (range, 16.0-23.0 mm). The mean transverse and longitudinal widths of the cortical notch were 3.0 mm (range, 1.6-4.5 mm) and 8.0 mm (range, 6.5-14.8 mm), respectively. The mean distance between the tip of the triceps insertion and the osteotomy apex was 22.0 mm (range, 18.0-24.0 mm) and the mean angle between the osteotomy surface and the vertical plane corresponding to the tangent plane was 20° (range, 10° to 25°). The mean angle of the V shape was 140° (range, 130° to 150°).

CONCLUSIONS

Using the narrowest edge lacking cartilage (lateral or medial side) as a point of reference to locate the bare area, the designed chevron osteotomy entered the joint in the bare area in most specimens and decreased associated damage to the joint cartilage.

CLINICAL RELEVANCE

This study describes the anatomy of the bare area and the design of the ideal chevron-shaped osteotomy to treat type C distal humerus fractures.

Controversies in Fractures of the Proximal Ulna

The olecranon process, coronoid process, and greater sigmoid notch are important components of the complex proximal ulna. Along with providing bony stability to the ulnohumeral joint, the proximal ulna serves as the attachment site of many important muscles and ligaments that impart soft tissue stability to the elbow joint. Management of proximal ulnar fractures continues to evolve as advances in imaging and anatomic and biomechanical studies have led to improvements in available implants; however, controversies remain, as shown in the current relevant literature.