Cell Count and Cell Density Decrease as Age Increases in Cadaveric Pediatric Medial Menisci.

Purpose: To examine the histologic changes in terms of cellularity, cell density, and nuclear shape in medial meniscal cellularity during skeletal development using pediatric cadaver specimens.

Methods: Medial menisci from 26 pediatric cadavers, 11 female and 15 male (total 36 menisci), were obtained from tissue bank. Mean age of female donors was 34 months (1-108 months) and of male donors was 52 months (1-132 months).

Stress-deprivation induces an up-regulation of versican and connexin-43 mRNA and protein synthesis and increased ADAMTS-1 production in tendon cells .

: The proper function of the tenocyte network depends on cell-matrix as well as intercellular communication that is mechanosensitive. Building on the concept that the etiopathogenic stimulus for tendon degeneration is the catabolic response of tendon cells to mechanobiologic under-stimulation, we studied the pericellular matrix rich in versican and its predominant proteolytic enzyme ADAMTS-1, as well as Connexin-43 (Cx43), a major gap junction forming protein in tendons, in stress-deprived rat tail tendon fascicles (RTTfs).: RTTfs were stress-deprived for up to 7 days under tissue culture conditions.

Hypoxia inhibits primary cilia formation and reduces cell-mediated contraction in stress-deprived rat tail tendon fascicles.

Background: Hypoxia, which is associated with chronic tendinopathy, has recently been shown to decrease the mechanosensitivity of some cells. Therefore, the purpose of this study was to determine the effect of hypoxia on the formation of elongated primary cilia (a mechanosensing organelle of tendon cells) and to determine the effect of hypoxia on cell-mediated contraction of stress-deprived rat tail tendon fascicles (RTTfs).

Methods: Tendon cells isolated from RTTfs were cultured under normoxic (21% O) or hypoxic (1% O) conditions for 24 hours.

Crimp length decreases in lax tendons due to cytoskeletal tension, but is restored with tensional homeostasis.

Collagen crimp morphology is thought to contribute to the material behavior of tendons and may reflect the local mechanobiological environment of tendon cells. Following loss of collagen tension in tendons, tenocytes initiate a contraction response that shortens tendon length which, in turn, may alter crimp patterns. We hypothesized that changes in the crimp pattern of tendons are the result of cell-based contractions which are governed by relative tautness/laxity of the collagen matrix.

Histologic Evaluation of Biopsy Specimens Obtained After Rotator Cuff Repair Augmented With a Highly Porous Collagen Implant.

Purpose: To histologically evaluate biopsy specimens from patients who previously underwent rotator cuff repair augmented with a highly porous collagen implant.

Methods: Biopsies of collagen implant/host-tissue constructs were obtained from 7 patients undergoing a second arthroscopic procedure at various time periods (5 weeks to 6 months) after arthroscopic rotator cuff repair augmented with a collagen implant overlay. The biopsy specimens were examined histologically for host-tissue ingrowth, host-tissue maturation, and host-implant biocompatibility.

Evidence of healing of partial-thickness rotator cuff tears following arthroscopic augmentation with a collagen implant: a 2-year MRI follow-up.

Background: partial-thickness rotator cuff tears frequently enlarge due to increased local strain and often progress to full-thickness tears. Studies suggest the addition of new tendinous tissue to injured cuff tendons would significantly decrease peak strain, possibly protecting against tear progression. The aim of this study was to assess the ability of a highly-porous collagen implant to induce new tissue formation and limit tear progression when placed on the bursal surface of partial-thickness cuff tears.

Preliminary investigation of a biological augmentation of rotator cuff repairs using a collagen implant: a 2-year MRI follow-up.

Background: the inability to restore the normal tendon footprint and limit strains on the repair site are thought to contribute to re-tearing following rotator cuff repair. The purpose of this study was to use a collagen implant to augment rotator cuff repairs through the restoration of the native tendon footprint and the induction of new tissue to decrease overall tendon strain.

Methods: repairs of full-thickness rotator cuff lesions in 9 adult patients were augmented with a novel collagen implant placed over the bursal surface of the repair.

Increased susceptibility of skin from HERDA (Hereditary Equine Regional Dermal Asthenia)-affected horses to bacterial collagenase degradation: a potential contributing factor to the clinical signs of HERDA.

Background: Hereditary equine regional dermal asthenia (HERDA) is a genetic disorder of collagen resulting in fragile, hyper-extensible skin and ulcerative lesions. The predominance of skin lesions have been shown to occur on the dorsum of HERDA-affected horses. While this has been postulated to be due to increased exposure to sunlight of these areas, the precise pathological mechanism which causes this to occur is unclear.

High magnitude, in vitro, biaxial, cyclic tensile strain induces actin depolymerization in tendon cells.

Background: the cytoskeleton is a dynamic arrangement of actin filaments that maintain cell shape and are vital in mediating the mechanobiological response of the cell.

Methods: to determine the cytoskeletal response to varying in vitro, biaxial stretch amplitudes, rat-tail tendon cells were paired into control and cyclically strained groups of 4.75, 9.

Thermal energy enhances cell-mediated contraction of lax rat tail tendon fascicles following exercise.

Background: the application of thermal energy (TE) has shown promise in the treatment of tendinopathy. However, the precise mechanism(s) of action of this therapy is unclear. The loss of tendon cell homeostatic tension, due to loading-induced laxity, produces catabolic changes associated with tendinopathy.

Tendon mechanobiology: Current knowledge and future research opportunities.

Tendons mainly function as load-bearing tissues in the muscloskeletal system; transmitting loads from muscle to bone. Tendons are dynamic structures that respond to the magnitude, direction, frequency, and duration of physiologic as well as pathologic mechanical loads via complex interactions between cellular pathways and the highly specialized extracellular matrix. This paper reviews the evolution and current knowledge of mechanobiology in tendon development, homeostasis, disease, and repair.

Allografts in soft tissue reconstructive procedures: important considerations.

Context: Allografts offer several important advantages over autografts in musculoskeletal reconstructive procedures, such as anterior cruciate ligament reconstruction. Despite growing widespread use of allograft tissue, serious concerns regarding safety and functionality remain. We discuss the latest knowledge of the potential benefits and risks of allograft use and offer a critical review of allograft tissue regulation, management, and sterilization to enable the surgeon to better inform athletes considering reconstructive surgery options.

Tendon Contraction After Cyclic Elongation Is an Age-Dependent Phenomenon: In Vitro and In Vivo Comparisons.

Background: Tendons are viscoelastic tissues that deform (elongate) in response to cyclic loading. However, the ability of a tendon to recover this elongation is unknown.

Hypothesis: Tendon length significantly increases after in vivo or in vitro cyclic loading, and the ability to return to its original length through a cell-mediated contraction mechanism is an age-dependent phenomenon.

Tissue-engineered augmentation of a rotator cuff tendon using a reconstituted collagen scaffold: a histological evaluation in sheep.

To determine if an absorbable collagen scaffold of high porosity would allow rapid tissue in-growth and permit the functional maturation and alignment of tendon-like tissue, scaffolds were sutured to the superficial surface of the infraspinatus tendons of adult sheep. Histology demonstrated complete ingrowth with fibrovascular tissue by 6 weeks and by 12 weeks the scaffold had induced the formation of a layer of dense, regularly-oriented collagenous tissue which significantly increased the thickness of the native tendon. This new tissue was well-integrated into the host tissues at both the bone interface and along the length of the tendon.

Tendon cell ciliary length as a biomarker of in situ cytoskeletal tensional homeostasis.

To determine if tendon cell ciliary length could be used as a biomarker of cytoskeletal tensional homeostasis, 20 mm long adult rat tail tendons were placed in double artery clamps set 18 mm apart to create a 10% laxity. The tendons were allowed to contract over a 7 day period under culture conditions. At 0, 1, 5, and 7 days the tendon cell cilia were stained and ciliary length measured using confocal imaging.

Microvasculature of the suspensory ligament of the forelimb of horses.

Objective: To determine the microvascular anatomy of the suspensory ligament of the forelimb of horses.

Sample: 17 cadaveric forelimbs from 9 adult horses with no known history of forelimb lameness.

Procedures: The median artery of the forelimb was cannulated proximal to the antebrachiocarpal joint and injected with contrast medium for CT evaluation of the gross vasculature (n = 2) or India ink to evaluate the microvasculature (12).

The basic science of platelet-rich plasma (PRP): what clinicians need to know.

Platelet-rich plasma (PRP) has been advocated for the biological augmentation of tissue healing and regeneration through the local introduction of increased levels (above baseline) of platelets and their associated bioactive molecules. In theory, the increased levels of autologous growth factors and secretory proteins provided by the concentrated platelets may enhance the wound healing process, especially in degenerative tissues or biologically compromised individuals. Although PRP has been increasingly utilized in the treatment of a variety of sports-related injuries, improvements in healing and clinical outcomes have not been universally reported.

Arthroscopic single-row versus double-row rotator cuff repair: a meta-analysis of the randomized clinical trials.

Purpose: The purpose of this meta-analysis was to critically assess whether there are differences in clinical outcomes between single-row and double-row rotator cuff repair in prospective randomized Level I studies.

Methods: Using Medline, Scopus, Scirus, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and the Cochrane Library, as well as a hand search, we searched for randomized prospective trials comparing single-row and double-row rotator cuff repair. The functional outcome scores included the American Shoulder and Elbow Surgeons shoulder scale, the Constant shoulder score, and the University of California, Los Angeles shoulder rating scale.

Age-related changes in the cellular, mechanical, and contractile properties of rat tail tendons.

Tendon laxity following injury, cyclic creep, or repair has been shown to alter the normal homeostasis of tendon cells, which can lead to degenerative changes in the extracellular matrix. While tendon cells have been shown to have an inherent contractile mechanism that gives them some ability to retighten lax tendons and reestablish a homeostatic cellular environment, the effect of age on this process is unknown. To determine the effect of aging on cell number, cell shape, and tensile modulus on tendons as well as the rate of cell-mediated contraction of lax tendons, tail tendon fascicles from 1-, 3-, and 12-month-old rats were analyzed.

Peak impact accelerations during track and treadmill running.

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time.

Age-dependent effects of systemic administration of oxytetracycline on the viscoelastic properties of rat tail tendons as a mechanistic basis for pharmacological treatment of flexural limb deformities in foals.

Objective: To describe the effect of systemically administered oxytetracycline on the viscoelastic properties of rat tail tendon fascicles (TTfs) to provide a mechanistic rationale for pharmacological treatment of flexural limb deformities in foals.

Sample: TTfs from ten 1-month-old and ten 6-month-old male Sprague-Dawley rats.

Procedures: 5 rats in each age group were administered oxytetracycline (50 mg/kg, IP, q 24 h) for 4 days.

Analysis of the basic science section of the orthopaedic in-training examination.

Since 1963, the Orthopaedic In-Training Examination (OITE) has been administered to orthopedic residents to assess residents' knowledge and measure the quality of teaching within individual programs. The OITE currently consists of 275 questions divided among 12 domains. This study analyzed all OITE basic science questions between 2006 and 2010.

Re-establishment of cytoskeletal tensional homeostasis in lax tendons occurs through an actin-mediated cellular contraction of the extracellular matrix.

Cytoskeletal tensional homeostasis is known to be an important factor in controlling catabolic gene expression in tendon cells. Loss of cell tension in lax rat tail tendon fascicles (RTTfs) has been associated with an upregulation of MMP-13 gene expression and protein synthesis. To determine the role of the actin cytoskeleton in re-establishing tensional homeostasis in lax tendons, RTTfs were allowed to freely contract in vitro for 8 days.

Comparison of the acute inflammatory response of two commercial platelet-rich plasma systems in healthy rabbit tendons.

Background: Numerous studies have shown platelet-rich plasma (PRP) preparations differ with respect to the inclusion of certain blood components, which may affect the host's cellular response.

Hypothesis: This study evaluated the inflammatory effect of Biomet GPS III leukocyte-rich PRP (LR-PRP) versus MTF Cascade leukocyte-poor PRP (LP-PRP) after intratendinous injection in an animal model. The authors anticipated that LR-PRP would incite a greater acute inflammatory response than LP-PRP.