The oblique cord of the forearm in man

Radial head distalisation with an external ring fixator as a therapy option in children with chronic posttraumatic radiocapitellar dislocations

PURPOSE

Missed monteggia-type injuries in children can result in chronic radial head dislocation with anatomic changes and osteoarticular remodeling of the radial head. In later stages, joint reconstruction is impossible and a functional radial head distalization can be a therapy option in symptomatic patients.

METHODS

From 2010 to 2018, 46 patients (18 female and 28 male, mean age 11.8 (4-20)) with chronic radius head dislocation treated in our institution were retrospectively analyzed. A radial head distalization was performed in symptomatic patients at the time of ulna lengthening and angulation by use of an external ring fixator. We analyzed the surgical and radiographic data as well as the clinical outcome of the patients measured by DASH and Mayo Elbow score.

RESULTS

16 patients (6 female, 10 male) fulfilled the criteria for functional radial head distalization. Main reason was Monteggia injury in 11 cases, and radial head fracture in 5 cases. Average follow-up was 5.1 years (range 1-9, SD 2.1). Mean time from injury was 4.14 years (range: 4 months to 12 years, SD 3.5 years). Mean duration of external fixation was 106 days (range 56-182, SD 31.2), lengthening was 21.3 mm (range 12-42, SD 8.8). Average degree of sagittal angulation 14.8° (0-32°, SD 10.7°), coronal angulation 4.4° (0-25°, SD 7.3°). DASH score showed a good result with 2.4, and the MAYO Elbow Score was excellent (95/100). No secondary luxation of the radius head was detected.

CONCLUSION

Radial head distalization with external ring fixator can be a therapy option for chronic radius head dislocations in symptomatic patients without losing stability of the elbow joint in contrast to radial head resection.

Monteggia fractures: analysis of patient-reported outcome measurements in correlation with ulnar fracture localization

BACKGROUND

Monteggia fractures and Monteggia-like lesions result after severe trauma and have high complication rates. Preliminary biomechanical studies suggested a correlation between ulnar fracture localization and clinical result.

OBJECTIVES

Key objective was to evaluate whether the site of the ulnar fracture can be correlated to clinical outcome after open reduction and internal stabilization.

METHODS

In a retrospective, monocentric study 35 patients who underwent surgical treatment after suffering a Monteggia injury or Monteggia-like lesion were included. Fractures were classified according to Bado and Jupiter, the site of the fracture location at the proximal ulna and regarding the potential accompanying ligamentary injury. In a follow-up examination validated patient-reported outcome measures and functional parameters were evaluated. Furthermore, treatment strategy and complications were analysed.

RESULTS

Mean patient age was 51.9 years (± 18.0). 69% were females (n = 24). Follow-up took place after 50.5 months (± 22.1). Fractures were classified according to Bado (I:2, II:27, III:4, IV:2). Bado II-fractures were further classified according to Jupiter (A:7, B:16, C:3, D:1). Cases were divided into subgroups depending upon the distance of the ulnar fracture site in respect to its distal endpoint (A: < 7 cm and B: > 7 cm). Average overall MEPS was 84.1 (± 19.0). Oxford elbow score and DASH were 37.2 (± 10.5) and 20.4 (± 20.5). Average extension capability reached - 7° (± 7.5). Mean flexion was 134.8° (± 19.7). Average pain according to visual analogue scale was 1.6 (± 1.9). We found no differences between the subgroups regarding the PROMs. Subgroup A displayed a worse extension capability (p = 0.027) and patients were significantly older (p < 0.01). Comparing patients with and without fracture of the radial head, we observed no differences. Patients with an accompanying injury of the coronoid process displayed higher pain levels (p = 0.011), a worse functionality (p = 0.027) and overall lower scoring in PROM.

CONCLUSION

The presented results suggest that in Monteggia fractures and Monteggia-like lesions, the localization of the ulna fracture can give a hint for its postoperative outcome. However, we could not confirm the hypothesis of an increasing instability in ulnar fractures located further distally (high severity of the potential ligamentous injury). Intraarticular fractures or injuries with a close relation to the joint have a worse prognosis, especially if the coronoid process is injured. Trial registration Registration was done with ClinicalTrials.gov under NCT05325268.

Structural topography of the interosseous membrane of the human forearm

The aim of this study was to evaluate the morphology of the six different parts of the interosseous membrane (IOM) in 11 human cadaver forearms, including the distal oblique bundle (DOB), the distal accessory band (DAB), the central band (CB), the proximal accessory band (PAB), the dorsal oblique accessory cord (DOAC), and the proximal oblique cord (POC). Hematoxylin-eosin and Elastica van Gieson stained slices were used to investigate the tissue morphology. The DOB and DOAC were absent in one IOM and the POB in two IOMs, respectively. The CB and DAB were longer than all other structures except for each other. The DOAC was longer than the DOB. The DAB, CB, and PAB, were broader than the DOB, DOAC, and POC. No significant differences were observed regarding structure thickness. All structures were found to consist of densely packed parallel collagen fiber arrangement. The DOB and POC had a higher amount of elastic fibers in the fascicular collagen tissue than the other structures. Elastic fibers were more often equally distributed throughout the structures than condensed epifascicular or at the insertion into bone. The tight parallel collagen composition within the different structures reflects the central stabilizing role of the IOM in the forearm. The higher amount of elastic fibers within the DOB and POC can be attributed to their location close to the distal and proximal radioulnar joints, respectively. Here elastic fibers allow adaption to forearm rotation, whereas the structures of the central part of IOM have less elasticity reflecting the predominant stabilizing function.

Predictive factors for re-displacement in diaphyseal forearm fractures in children-role of radiographic indices

Background and purpose - Manipulation and cast immobilization is the primary management for diaphyseal forearm fractures in children, and re-displacement is the most common complication. We wanted (1) to analyze the incidence of re-displacement in a group of children treated with close reduction and casting; (2) to determine predictive factors such as demographics, mechanism of injury, affected bone, fracture pattern, degree of initial displacement and angulation, and reduction accuracy; and (3) to determine the prognostic effect of previously defined radiographic indices. Patients and methods - We prospectively studied 269 consecutive children with closed and complete middle-third diaphyseal fractures treated with close reduction and casting from October 2014 to April 2015. Factors analyzed included demographics, initial fracture features, having a non-anatomical reduction, and the radiographic indices of cast quality. Results - There were 189 fractures of both bones (70%) and 80 solitary fractures (30%). The overall re-displacement rate was 11%. According to multivariable analysis, independent predictors of re-displacement were initial angulation >10° (RR =5) and failure to achieve an anatomical reduction (RR =2). Statistically significant radiographic indices regarding increased rate of re-displacement included cast index ≥0.7 (RR =5), Canterbury index ≥1.1 (RR =3), and 3-point index ≥0.8 (RR =6). Interpretation - Our results suggested that fractures with a higher degree of initial angulation and non-anatomical reduction more often result in re-displacement. Moreover, the casting quality examined with the radiographic indices played an important role in the success of a non-operative management.

The middle radioulnar joint and triarticular forearm complex

The forearm is composed of the radial and ulnar shafts, which are linked by the interosseous membrane and intercalated between the elbow and wrist. The radius and ulna are connected by three joints, the proximal, middle, and distal radioulnar joints. The forearm ensures pronation/supination and longitudinal load transfer. The biomechanical and clinical relevance of the proximal and distal radioulnar joints is well established. In contrast, the middle radioulnar joint was considered relatively unimportant until studies published in the last decade showed that it fulfils crucial biomechanical functions and is of considerable clinical significance. We believe the conventional concept in which the forearm is viewed as part of either the elbow or the wrist is outdated and that a more relevant concept describes the forearm as a triarticular complex that functions as a full-fledged entity. In this concept, the three forearm radioulnar joints (proximal, middle, distal) work together to provide stability, mobility and load transfer. Here, we will argue for the relevance of the triarticular complex concept based on published data about forearm biomechanics and pathological conditions.

Interosseous membrane of the forearm: length change of ligaments during forearm rotation

PURPOSE

An earlier anatomic study described five ligamentous components in the interosseous membrane of the forearm (central band, accessory band, distal oblique bundle, proximal oblique cord, and dorsal oblique accessory cord) and provided their precise location of attachment. In the present study, we investigated in vivo length changes of these five ligaments during forearm rotation to understand the function of each ligament.

METHODS

We acquired computed tomographies of nine forearms from seven healthy volunteers for 3 rotation positions: maximum pronation, neutral position, and maximum supination. We created 3-dimensional models of the radius, ulna, and the 5 ligaments by combining osseous images and anatomic data of ligament attachment. We calculated 3-dimensional ligament lengths between attachments during forearm rotation using a markerless bone registration technique. We also examined relationships between the axis of forearm rotation and each ligament.

RESULTS

The distal 3 ligaments (central band, accessory band, and distal oblique bundle) had little change in length during forearm rotation, with their ulnar attachments located almost on the axis of forearm rotation. The 2 proximal ligaments (proximal oblique cord and dorsal oblique accessory cord) changed substantially in length, with their attachments out of the course of the axis.

CONCLUSIONS

The distal 3 ligaments of the interosseous membrane are essentially isometric stabilizers of the forearm. The distal oblique bundle in the distal membranous portion may stabilize the distal radioulnar joint in 40% of human subjects who have this ligament.

Interosseous membrane of the forearm: an anatomical study of ligament attachment locations

PURPOSE

The interosseous membrane (IOM) of the forearm is a stout ligamentous complex that reportedly comprises several ligamentous components. The purpose of this cadaveric study was to define all IOM ligaments and to clarify the precise attachment locations.

METHODS

Thirty forearms from 15 embalmed cadavers were used. After dissection, all IOM ligaments were identified, and attachments were measured from the tip of the radial styloid or the ulnar head. Attachment locations were represented as a percentage of total bone length from the distal end of the radius or ulna.

RESULTS

The IOM included 5 kinds of ligaments: central band, accessory band, distal oblique bundle, proximal oblique cord, and dorsal oblique accessory cord. The most distal and proximal ends of the radial origin of the central band were 53% and 64% of total radial length from the tip of the radial styloid, whereas those of the ulnar insertion were 29% and 44% of total ulnar length from the ulnar head. The center point of the radial origin and ulnar insertion of the accessory band were 37% and 23%, respectively. The center points of the ulnar origins and radial insertions were 15% and 10% for the distal oblique bundle; 80% and 79% for the proximal oblique cord; and 64% and 62% for the dorsal oblique accessory cord, respectively.

CONCLUSIONS

The present study clarified precise attachment locations of all representative IOM ligaments. This information will be useful in planning proper graft placement in ligament reconstruction surgery and for future biomechanics research into the function of the IOM ligaments.