Form and function of the oblique cord (chorda obliqua) in anthropoid primates

Maximum longevity and juvenile mortality in zoo-housed mangabeys

Little is known about the biology of grey-cheeked and black crested mangabeys (Lophocebus albigena and Lophocebus aterrimus, respectively). As these primates face threats in the wild, well-monitored zoo-housed populations with up to date registries are becoming increasingly valuable to acquire species knowledge and to support conservation efforts. We used international studbooks to extract demographic and genetic information on 519 mangabeys to investigate how life history and parent-related variables influence maximum longevity and juvenile mortality. Generalized linear mixed models, as well as survival analyses, were applied. Results showed that females lived significantly longer than males, which is not uncommon in primates. Furthermore, our results indicated that the maximum longevity is lower for individuals living in European zoos versus individuals from North American zoos, which may be due to a combination of environmental differences and potential founder effects. We also show that the maternal maximum longevity is positively related to the maximum longevity of the offspring, which may be explained by the inheritance of "good genes". However, the age of the mother at the moment of birth was negatively related to the maximum longevity of the offspring, which contradicts literature that states that, in primates, more experienced and thus older mothers will raise their offspring better than less experienced mothers. Instead, it is more likely that an "optimal age range" exists for breeding mothers. Our study provides insights into the population biology of captive mangabeys and may be helpful for identifying future research priorities to optimize primate health and welfare directly ex situ, and indirectly in situ.

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.

Forearm Interosseous Ligaments: Anatomical and Histological Analysis of the Proximal, Central, and Distal Bands

PURPOSE

To characterize and compare the histological structure of the proximal, central, and distal bands of the interosseous membrane (IOM) of the human forearm in fresh-frozen specimens.

METHODS

The IOMs from 16 fresh-frozen left forearm specimens were carefully dissected and examined. The footprint areas of the proximal, central, and distal IOM bands were measured in 6 specimens. The histological characteristics of the IOM bands were evaluated using hematoxylin-eosin and Masson trichrome staining protocols in 10 specimens as histological analysis necessitated an intact footprint. The footprint areas of the IOM were measured using an image processing program. The insertion complex was assessed using a light microscope.

RESULTS

Histological assessment revealed that the IOM structure demonstrated similarities with ligament structure. The average footprint areas of the proximal, central, and distal bands at the radial site were 11.1 ± 0.8, 180.4 ± 30.4, and 10.7 ± 1.3 mm², respectively. At the ulnar site, they were 11.0 ± 1.1, 171.8 ± 30.1, and 10.7 ± 1.2 mm², respectively. The insertion complex of the IOM into the bone comprised 4 layers: (1) interwoven collagen, (2) oblique collagen, (3) mineralized fibrocartilage (tidemark), and (4) lamellar bone. The average tidemark zone thicknesses of the proximal, central, and distal bands were 20.1 ± 6.3, 107.8 ± 22.9, and 20.6 ± 4.7 μm, respectively at the radial site and 12.0 ± 4.5, 85.7 ± 23.2, and 13.5 ± 6.9 μm, respectively at the ulnar site.

CONCLUSIONS

In this study, we confirm that the histological characteristics of the IOM are similar to those of ligaments. Compared with the proximal and distal bands, the central band has a greater footprint area and thicker tidemark zone.

CLINICAL RELEVANCE

If surgical reconstruction is performed, the size and histological characteristics of the graft should be similar to those of the native ligaments.

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.

In vivo three-dimensional motion analysis of chronic radial head dislocations

BACKGROUND

Forearm kinematics and interosseous membrane function in chronic radial head dislocations sustained in childhood are unknown. Several procedures have been performed to reduce the radial head on the basis of static preoperative assessment in only one forearm position, but clinical results are not always favorable.

QUESTIONS/PURPOSES

We investigated the in vivo three-dimensional (3D) kinematics and length changes of interosseous membrane ligaments during forearm rotation in chronic radial head dislocations using 3D CT registration techniques.

METHODS

We examined 10 patients with chronic radial head dislocations (seven Type 1 and three Type 4 Monteggia lesions). To quantify kinematics, the axis of rotation (AOR) and radial head motion were investigated using computer bone models constructed from CT data placing the forearm in three positions. We also created six interosseous membrane ligaments and calculated their 3D lengths during forearm rotation.

RESULTS

In Type 1 lesions, the AOR was located 2.4 mm from the center of the radial head (COR). The COR translated 2.8 mm sagittally and 3.4 mm coronally. Three interosseous membrane ligaments showed little change in length. In Type 4 lesions, the AOR was located 6.2 mm from the COR. The COR translated 10.2 mm sagittally and 4.7 mm coronally. No ligament showed an isometric pattern.

CONCLUSIONS

In Type 1 lesions, the radial head showed relatively stable motion in the dislocated position and the isometricity of the interosseous membrane remained, which supports the concept of ulnar osteotomy. Conversely, the radial head was unstable and the normal interosseous membrane ligament tautness pattern was disrupted in Type 4 lesions.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Studying primate carpal kinematics in three dimensions using a computed-tomography-based markerless registration method

The functional morphology of the wrist pertains to a number of important questions in primate evolutionary biology, including that of hominins. Reconstructing locomotor and manipulative capabilities of the wrist in extinct species requires a detailed understanding of wrist biomechanics in extant primates and the relationship between carpal form and function. The kinematics of carpal movement, and the role individual joints play in providing mobility and stability of the wrist, is central to such efforts. However, there have been few detailed biomechanical studies of the nonhuman primate wrist. This is largely because of the complexity of wrist morphology and the considerable technical challenges involved in tracking the movements of the many small bones that compose the carpus. The purpose of this article is to introduce and outline a method adapted from human clinical studies of three-dimensional (3D) carpal kinematics for use in a comparative context. The method employs computed tomography of primate cadaver forelimbs in increments throughout the wrist's range of motion, coupled with markerless registration of 3D polygon models based on inertial properties of each bone. The 3D kinematic principles involved in extracting motion axis parameters that describe bone movement are reviewed. In addition, a set of anatomically based coordinate systems embedded in the radius, capitate, hamate, lunate, and scaphoid is presented for the benefit of other primate functional morphologists interested in studying carpal kinematics. Finally, a brief demonstration of how the application of these methods can elucidate the mechanics of the wrist in primates illustrates the closer-packing of carpals in chimpanzees than in orangutans, which may help to stabilize the midcarpus and produce a more rigid wrist beneficial for efficient hand posturing during knuckle-walking locomotion.

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.

The oblique cord of the forearm in man

There is minimal and often conflicting data in the literature regarding the oblique cord of the forearm. The current study seeks to elucidate further the anatomy of this structure of the upper extremity. In adult cadavers, the oblique cord was observed for and, when found, measurements were made of it. Ranges of motion were carried out while observation of the oblique cord was made. An oblique cord was found on 52.6% of sides. Gantzer's muscle was found on 55% of sides and, when present, had attachment into the oblique cord on five sides. The oblique cord was present on 13 sides with a Gantzer's muscle. Of the 20 sides with an oblique cord, no Gantzer's muscle was found on 10. The mean length of the oblique cord was 3.4 cm. In the majority of specimens, this cord tapered from proximal to distal. The proximal, middle, and distal widths of this structure had means 9, 7, and 4 mm, respectively. The oblique cord was found to travel approximately 45 degrees from a line drawn through the ulna and more or less traveled perpendicular to the insertion site of the bicipital tendon. This ligament was lax in the neutral position and with pronation became lax in all specimens. The oblique cord progressively became taut with increased supination from the neutral position and was maximally taut with the forearm fully supinated. Tautness of this cord was also found with distal distraction of the radius. Following the transection of the oblique cord, no discernable difference was observed in regard to maximal supination of the forearm or distal distraction of the radius. No obvious instability of the proximal forearm was found following transection of the oblique cord. Functionally, although the oblique cord may resist supination, it is unlikely that this structure affords significant stability to the proximal forearm, as it was often absent, of a very small caliber, and based on our observations, following its transection, the amount of supination of the forearm did not increase. Moreover, one would expect that this structure would never resist supination alone, as the larger overlying muscles would become taut prior to calling upon the action of this cord. Based on our findings, the function of the oblique cord appears insignificant in providing significant stability to the proximal forearm; however, further investigative studies are now necessary to confirm these data.