Effect of radial head malunion on radiocapitellar stability

Isolated Proximal Radioulnar Joint Instability: Anatomy, Clinical Presentation, and Current Treatment Options

Isolated proximal radioulnar joint instability is an uncommon and often challenging problem that may manifest as recurrent instability of the proximal aspect of the radius, usually during forearm pronation and supination. Instability is due to deficiency of the stabilizing structures around the proximal aspect of the radius, and biomechanical studies have highlighted the importance of the annular ligament and the interosseous membrane in both transverse and longitudinal plane stability. Reconstruction of the stabilizing structures around the radial head often is indicated in cases of recurrent instability and includes joint-preserving procedures such as annular ligament reconstruction, proximal ulnar osteotomy, and interosseous membrane reconstruction. Rarely, salvage procedures such as interpositional arthroplasty or 1-bone forearm reconstruction are necessary. A thorough understanding of the anatomic structures that stabilize the proximal aspect of the radius and the complexities of forearm biomechanics is required in order to successfully diagnose and manage this condition.

Proximal Radius Fractures in Children

Fractures of the proximal radius represent 5% to 10% of all elbow fractures in children. These fractures have many treatment options and have a high risk of complication, particularly loss of forearm rotation. Nonsurgical management of minimally displaced radial neck fractures produces excellent results in most patients. For displaced fractures, numerous methods of closed and percutaneous reduction have been proposed, whereas open reduction has been associated with particularly poor outcome. Many additional factors, including fracture angulation, patient age, associated injury, articular involvement, and internal fixation, may lead to worse outcomes. Because the literature is limited to retrospective case series, few studies provide high-level evidence to guide the treatment of pediatric proximal radius fractures; however, certain management principles have been established that are reviewed here.

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.

Ulnohumeral dislocation despite intact radiocapitellar joint: a rare Monteggia variant

We treated one patient with a mid-diaphyseal radius fracture and concomitant anteromedial facet fracture of the coronoid. The ulnohumeral joint was severely unstable by complete ligament detachment and interosseous membrane rupture. Despite this gross instability, the radiocapitellar was congruent and stable. The possible mechanism of radiocapitellar stability is discussed and the concept of concavity-compression stability across the radiocapitellar joint is emphasized.

Radiocapitellar contact characteristics during prosthetic radial head subluxation

BACKGROUND

Metallic radial head prostheses are often used in the management of comminuted radial head fractures and elbow instability. We hypothesized that during radiocapitellar subluxation, the contact pressure characteristics of an anatomic radial head prosthesis will more closely mimic those of the native radial head compared with a monopolar circular or a bipolar circular radial head design.

MATERIALS AND METHODS

With use of 6 fresh frozen cadaver elbows, mean radiocapitellar contact pressures, contact areas, and peak pressures of the native radial head were assessed at 0, 2, 4, and 6 mm of posterior subluxation. These assessments were repeated after the native radial head was replaced with anatomic, monopolar circular and bipolar circular prostheses.

RESULTS

The joint contact pressures increased with the native and the prosthetic radial head subluxation. The mean contact pressures for the native radial head and anatomic prosthesis increased progressively and significantly from 0 to 6 mm of subluxation (native, 0.6 ± 0.0 MPa to 1.9 ± 0.2 MPa; anatomic, 0.7 ± 0.0 MPa to 2.1 ± 0.3 MPa; P < .0001). The contact pressures with the monopolar and bipolar prostheses were significantly higher at baseline and did not change significantly further with subluxation (monopolar, 2.0 ± 0.1 MPa to 2.2 ± 0.2 MPa [P = .31]; bipolar, 1.7 ± 0.1 MPa to 1.9 ± 0.1 MPa [P = .12]). The pattern of increase in contact pressures with the anatomic prosthesis mimicked that of the native radial head. Conversely, the circular prostheses started out with higher contact pressures that stayed elevated.

CONCLUSION

The articular surface design of a radial head prosthesis is an important determinant of joint contact pressures.

Regional Variations in Cartilage Thickness of the Radial Head: Implications for Prosthesis Design

PURPOSE

To characterize the regional variations in cartilage thickness around the radial head.

METHODS

We dissected 27 cadaveric radii and scanned them with computed tomography in neutral position. Three-dimensional cartilage and subchondral bone surface models were generated from computed tomography scans and 2 independent observers processed them through a computer program to obtain cartilage thickness measurements. These measurements were taken at 41 predetermined landmarks around the periphery of the radial head and within the articular dish.

RESULTS

At the periphery of the radial head, cartilage was thickest in the posteromedial region. Thickness values within the articular dish were similar but increased toward the rim. Regional variations within the rim (range, 0.76-1.73 mm) were also detected with the thickest region located anteriorly and thinnest region laterally. In addition, cartilage was significantly thicker in male relative to female specimens.

CONCLUSIONS

Regional variations in cartilage thickness are present around the periphery and rim and within the articular dish of the radial head.

CLINICAL RELEVANCE

Cartilage thickness across the articular dish may contribute to dish depth and the radius of curvature. This may be clinically important for the design of anatomic implants, because accounting for such subtle contours could help to restore radiocapitellar concavity-compression stability better.

The effect of capitellar impaction fractures on radiocapitellar stability

PURPOSE

To determine the effect of capitellar impaction fractures on radiocapitellar stability in a model that simulated a terrible triad injury.

METHODS

Six cadaveric elbows were dissected free of skin and muscles. Tendons were preserved. The lateral collateral ligament was released and repaired (surgical control). Two sizes of capitellar impaction defects were created. After lateral collateral ligament release and repair, we then sequentially created osseous components of a terrible triad injury (partial radial head resection and coronoid fracture) through an olecranon osteotomy that was fixed with a plate. Radiocapitellar stability was recorded after the creation of each new condition.

RESULTS

Significantly less force was required for radiocapitellar subluxation after the creation of 20° and 40° capitellar defects compared with the surgical control (intact capitellum). After the addition of a Mason type II radial head defect and then a coronoid defect, stability decreased significantly further.

CONCLUSIONS

Impaction fractures of the distal portion of the capitellum may contribute to a loss of radiocapitellar stability, particularly in an elbow fracture-dislocation.

CLINICAL RELEVANCE

Because these injuries may be unrecognized, consideration should be given to diagnosing and addressing them.

Surgical management of pediatric radial neck fractures

BACKGROUND

Management of pediatric radial neck fractures is controversial regarding acceptable alignment, variable reduction techniques, and suboptimal outcomes. The purpose of this study was to assess the characteristics, management, and results in a surgical cohort, in efforts to identify prognostic factors and offer treatment suggestions. It was hypothesized that less invasive reduction maneuvers would precede open reduction and that worse results would correlate with fracture severity, open reduction, and the presence of associated injuries.

METHODS

Retrospective analysis of 151 children in whom a radial neck fracture had been surgically treated from 2001 to 2011 was performed. The mean age (and standard deviation) and duration of follow-up were 8.4 ± 2.9 years and 13.3 ± 20.0 months, respectively; 40% of the patients were male. A successful clinical result was defined as elbow flexion of ≥120°, flexion contracture of <20°, forearm rotation of ≥90° with ≥45° of supination and pronation, and no complications.

RESULTS

An isolated radial neck fracture occurred in 54% of the children. The mean angulation and displacement improved from 43° ± 19° and 37% ± 35%, respectively, before treatment to 13° ± 7° and 0.9% ± 4% after treatment (p < 0.001). Twenty-two procedural combinations were used to treat these patients, and 67% of the open reductions were not preceded by percutaneous or closed reduction attempts. Among 131 patients with adequate follow-up, 31% had an unsuccessful outcome. An age of ten years or more (odds ratio [OR] = 5.85, p = 0.001), a time to surgery of two days or less (OR = 4.73, p = 0.02), and greater fracture displacement (OR = 1.25 per 10%, p = 0.001) were independent predictors of unsuccessful outcomes. Increased fracture severity and open reduction were associated with poor results, although the presence of concomitant injuries was not. It is predicted that closed manipulation will fail for half of fractures angulated ≥36°, and that half of fractures displaced ≥65% will require open reduction. The predicted frequency of unsuccessful outcomes is 50% with 76% displacement.

CONCLUSIONS

There continues to be great variation in the approach to treatment of displaced radial neck fractures in children. Suboptimal results occurred in 31% of the patients in this series, with worse results in patients older than ten years, who had increased fracture severity, and who underwent open reduction. Less invasive reduction methods should precede open reduction whenever possible.