Ibuprofen impairs capsulolabral healing in a rat model of anterior glenohumeral instability

Prevalence and clinical implications of heterotopic ossification after distal biceps tendon repair

Complete distal biceps tendon ruptures are relatively uncommon. Conservative treatment may result in persistent pain and weakness. Therefore, surgical repair is usually indicated in order to restore strength. Different surgical techniques and fixation methods have been described. The most reported complications after surgery are iatrogenic nerve damage, heterotopic ossification (HO) and re-rupture. Heterotopic ossification can be variable in size. Significant HO can limit range of motion while minor HO often remains asymptomatic. The overall presence of HO is likely underreported in literature, as imaging is reserved for symptomatic patients. The purpose of this study is to report the prevalence and clinical implications of heterotopic ossification after surgical repair of the distal biceps tendon. This retrospective study assessed the prevalence and clinical relevance of postoperative HO after distal biceps tendon repair. CT-scans were used to evaluate size and location of the HO. VAS scores, DASH scores, MEPI, and range of motion (ROM) were assessed to evaluate pain, patient satisfaction and elbow function. HO was observed on CT images of 19 out of 35 patients (54%). The use of interference screws, timing of surgery after rupture and timing of radiographic assessment postoperatively did not influence the prevalence of HO. The presence of HO had no statistically significant impact on the VAS scores, ROM measurements and MEPI and DASH scores. According to our findings, the overall incidence of HO is higher than previously reported but there are no differences in clinical outcomes when compared to patients without HO.

Biomolecule-releasing bioadhesive for glenoid labrum repair through induced host progenitor cell responses

Glenoid labral tears occur with repetitive dislocation events and are common injuries observed in shoulder arthroscopic procedures. Although surgery can restore shoulder anatomy, repair is associated with poor clinical outcomes, which may be attributed to the poor regenerative capability of glenoid labral fibrocartilage. Thus, this study was designed to assess whether in situ tissue regeneration via biomolecule-stimulated recruitment of progenitor cells is a viable approach for the regeneration of labral tears. We developed a click chemistry-based bioadhesive to improve labral repair and reduce local inflammatory responses due to trauma. Additionally, we previously identified the presence of progenitor cells in the human labrum, which can be recruited by platelet-derived growth factor (PDGF). Thus, we hypothesized that PDGF-releasing adhesives could induce the regenerative responses of progenitor cells at the injury site to improve labral healing. In a rat glenoid labral tear model, we evaluated the effect of PDGF-releasing adhesives on promoting progenitor cells to participate in labral tear healing. After 3 and 6 weeks, the labrum was histologically analyzed for inflammatory responses, progenitor cell recruitment, proliferation, and extracellular matrix (ECM) production (collagen and glycosaminoglycan). Our results showed that adhesives alone considerably reduced local inflammatory responses and labral tissue dissolution. PDGF-releasing adhesives significantly increased progenitor cell recruitment, proliferation, and ECM production. These results demonstrate that by accelerating autologous progenitor cell responses, PDGF-releasing adhesives represent a novel clinically relevant strategy to improve the healing of glenoid labral tears.

Common animal models lack a distinct glenoid labrum: a comparative anatomy study

Purpose

Development and validation of an animal model of labral healing would facilitate translation of novel surgical and biological strategies to improve glenolabral healing. The purpose of this study was to characterize the anatomic and histological properties of the shoulder labrum in rat, rabbit, dog, pig, goat, and humans. Given the demonstrated similarities in size and structural morphology in other joints, it was hypothesized that the goat glenoid with surrounding capsulolabral complex would most closely resemble that of humans in terms of dimensions and structure, as observed grossly and histologically.

Methods

Cadaveric glenohumeral joints from rats (n = 8), New Zealand white rabbits (n = 13), Mongrel dogs (n = 9), Spanish goats (n = 10), Yorkshire pigs (n = 10), and humans (n = 9) were freshly harvested. Photographs were taken of the glenoid with its surrounding capsulolabral complex. Linear dimensions of the glenoid articular surface were measured. It was determined where the capsulolabral complex was continuous with, or recessed from, the articular glenoid surface. The glenoid was divided into 6 equal segments radiating out toward 12, 2, 4, 6, 8, and 10 o’clock positions. Samples were sectioned and stained with Safranin O/Fast green and Mallory Trichrome. Insertion of the capsulolabral tissue onto the glenoid was qualitatively assessed and compared with gross morphology.

Results

Dimensions of the goat glenoid most closely paralleled dimensions of the human glenoid. A capsulolabral complex was continuous with the glenoid surface from ~ 9 to 12 o’clock in the rats, 7 to 12 o’clock in rabbits, 5 to 12 o’clock in the dogs, and 9 to 12 o’clock in goats, 6 to 12 o’clock in pigs, and 2 to 8 o’clock in humans. In contrast to humans, no other species demonstrated an organized fibrocartilaginous labrum either macroscopically or histologically.

Conclusion

The animals in the present study did not possess a discrete fibrocartilaginous labrum by gross or histological evaluation, as directly compared to humans. While models using these animals may be acceptable for examining other shoulder pathologies, they are not adequate to evaluate labral pathology.

Level of evidence

Basic Science Study; Anatomy and Histology; Cadaveric Animal Model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-021-00383-6.

Editorial Commentary: Reviewing the Science of Our Unscientific Criteria for Return to Sports After Shoulder Stabilization

In contrast to anterior cruciate ligament reconstruction, there is a paucity of primary studies that address the issue of return to play after anterior shoulder stabilization for glenohumeral instability. Most studies focused on clinical outcomes after anterior shoulder stabilization provide little detail on the authors' assessment protocols used in determining return to sport readiness. In fact, many issues germane to the postoperative rehabilitation process (biologic healing, motion recovery, strength recovery, and sport-specific considerations) remain poorly defined, and are not typically addressed using validated shoulder outcomes instruments. Sports medicine surgeons need more objective criteria on which to base their clinical decision making with athletes treated for anterior glenohumeral instability.