Long head biceps tenodesis with a knotless cinch suture anchor: a biomechanical analysis.

PURPOSE: The purpose of this study was to evaluate the initial fixation strength of 3 techniques of arthroscopic tenodesis of the long head of the biceps (LHB). METHODS: Eighteen human cadaveric shoulders were randomly assigned to one of 3 simulated arthroscopic biceps tenodesis techniques-simple suture (SS), Krakow stitch (KS), or lasso loop (LL)-combined with a knotless fixation implant (3.5-mm Piton Anchor; Tornier, Minneapolis, MN). Biomechanical parameters were evaluated by cyclic loading and load to failure. RESULTS: The mean failure load (P = .007) was 158.3 ± 32.2 N, 109.8 ± 41.1 N, and 46.6 ± 3.8 N for the KS, SS, and LL techniques, respectively. Mean stiffness was greater (statistically significant) in the KS (21.4 ± 3.0 N/mm) and SS (20.7 ± 7.9 N/mm) treatment groups compared with the LL group (4.5 ± 1.5 N/mm) (P = .011). CONCLUSIONS: Biceps tenodesis performed with a more secure tendon suturing technique, such as the Krakow technique, provides superior ultimate and fatigue strength and thus may be more secure in clinical application and yield better clinical results. The mechanical properties of the LL technique were especially poor in comparison. CLINICAL RELEVANCE: Although more complex suturing techniques for arthroscopic biceps tenodesis can be technically challenging, more secure tendon fixation may improve clinical outcomes.

Elbow arthritis and total elbow replacement.

Elbow arthritis is a relatively uncommon condition that can be successfully managed with non-operative and operative methods. The extent of pathologic involvement and severity of pain and dysfunction are the most important factors in selecting treatment. Arthroscopic, open, and arthroplasty surgery options provide successful outcomes in most cases.

Glenohumeral arthritis and total shoulder replacement.

Shoulder replacement surgery is a reliable procedure that provides predictable results in patients with all types of glenohumeral arthritis. When performed by an experienced surgeon for the right indications, and with appropriate physical therapy, dramatic improvements in pain and function are seen in the majority of patients. With the recent availability of the reverse prosthesis, even patients with rotator cuff deficiency may have pain relief and restoration of shoulder function after reverse shoulder arthroplasty.

Osterix/Sp7 regulates mesenchymal stem cell mediated endochondral ossification.

We investigated the expression and regulation of the zinc finger protein Osterix (Osx) during endochondral ossification in mice. In studies to determine the temporal and spatial regulation of Osx mRNA and protein during embryogenesis we found it to be present throughout development, but its expression is restricted to the immature chondro/osteoprogenitor cells and mature osteoblasts, excluding hypertrophic chondrocytes. Using a fracture model, we show a consistent pattern of Osx protein expression in mesenchymal progenitor cells in the periosteum and immature chondrocytes and osteoblasts embedded in the fracture callus. In contrast, hypertrophic chondrocytes, vessels and fibrous tissue were devoid of Osx expression. Additionally, using RNA isolated from fracture callus throughout the healing process, we observe that Osx transcripts parallel that of Runx2 and differentially overlap both cartilage and bone phenotypic markers. Furthermore, using limb bud-derived MLB13MYC Clone 17 cells, we show that PTHrP inhibited chondrocyte maturation while it enhanced mRNA levels of Osx in these chondro/osteoprogenitor cells. Gain and loss of function of Osx function experiments with these cells demonstrated that Osx serves as an inhibitor of chondrogenesis and chondrocyte maturation, while it promotes osteoblast maturation. Together, our findings provide the first demonstration of the molecular mechanisms underlying Osx inhibition of chondrocyte differentiation, and further suggest a role for this transcription factor in mediating endochondral ossification during bone repair.

Teriparatide (1-34 human PTH) regulation of osterix during fracture repair.

Based on remarkable success of PTH as an anabolic drug for osteoporosis, case reports of off-label use of teriparatide (1-34 PTH) in patients with complicated fractures and non-unions are emerging. We investigated the mechanisms underlying PTH accelerated fracture repair. Bone marrow cells from 7 days 40 microg/kg of teriparatide treated or saline control mice were cultured and Osx and osteoblast phenotypic gene expression assessed by real-time RT-PCR in these cells. Fractured animals injected daily with either saline or 40 microg/kg of teriparatide for up to 21 days were X-rayed and histological assessment performed, as well as immunohistochemical analyses of the Osx expression in the fracture callus. Osx, Runx2 and osteoblast or chondrocyte phenotypic gene expression was also assessed in fracture calluses. Our data shows that Osx and Runx2 are up-regulated in marrow-derived MSCs isolated from mice systemically treated with teriparatide. Furthermore, these MSCs undergo accelerated osteoblast maturation compared to saline injected controls. Systemic teriparatide treatments also accelerated fracture healing in these mice concomitantly with increased Osx expression in the PTH treated fracture calluses compared to controls. Collectively, these data suggest a mechanism for teriparatide mediated fracture healing possibly via Osx induction in MSCs.

Factors Expressed in an Animal Model of Anteroinferior Glenohumeral Instability.

BACKGROUND: There is little information on the molecular factors important in healing and changes that occur in the glenoid labrum in response to injury. Using a novel animal model of acute anterior shoulder dislocation, this study characterizes the factors expressed in the glenoid labrum in response to injury and correlates their expression to glenohumeral stability. PURPOSE: To study the response of the glenoid labrum to injury both biomechanically and with immunohistochemical testing. METHODS: An injury to the anteroinferior labrum was surgically induced in 50 male Lewis rats. Rats were sacrificed at 3, 7, 14, 28, or 42 days. Immunolocalization experiments were performed to localize the expression of growth factors and cytokines. For biomechanical testing, dynamic stiffness for anterior and posterior laxity, load to failure, stiffness, and maximum load were recorded. Statistical differences were determined at P < .05. STUDY DESIGN: Descriptive laboratory study. RESULTS: Expression of interleukin-1 beta (IL-1ß), transforming growth factor-beta 1 (TGF-ß1), matrix metalloproteinase 3 (MMP3), and matrix metalloproteinase 13 (MMP13) were increased in injured compared with uninjured specimens. Collagen III expression was increased early and decreased with time. Biomechanical testing verified instability by demonstrating increased anterior displacement and decreased stiffness in injured shoulders at all time points. CONCLUSION: This novel animal model of acute anterior shoulder dislocation showed increased expression of IL-1ß, TGF-ß1, MMP3, MMP13, and collagen III in the injured labral tissue at early time points. Increased anterior laxity and decreased stiffness and maximum load to failure were seen after anterior labral injury, supporting the model's ability to re-create anterior glenohumeral instability. These data provide important information on the temporal changes occurring in a rat model of anterior glenohumeral dislocation. CLINICAL RELEVANCE: Identification of factors expressed in the anterior capsule and glenoid labrum in response to injury may lead to the development of novel agents that can be used to augment glenoid labrum healing and ultimately improve both surgical and nonsurgical treatment of this common shoulder injury.