The effects of maturation and aging on the rotator cuff tendon-to-bone interface.

Rotator cuff tendon injuries often occur at the tendon-to-bone interface (i.e., enthesis) area, with a high prevalence for the elderly population, but the underlying reason for this phenomenon is still unknown. The objective of this study is to identify the histological, molecular, and biomechanical alterations of the rotator cuff enthesis with maturation and aging in a mouse model. Four different age groups of mice (newborn, young, adult, and old) were studied. Striking variations of the entheses were observed between the newborn and other matured groups, with collagen content, proteoglycan deposition, collagen fiber dispersion was significantly higher in the newborn group. The compositional and histological features of young, adult, and old groups did not show significant differences, except having increased proteoglycan deposition and thinner collagen fibers at the insertion sites in the old group. Nanoindentation testing showed that the old group had a smaller compressive modulus at the insertion site when compared with other groups. However, tensile mechanical testing reported that the old group demonstrated a significantly higher failure stress when compared with the young and adult groups. The proteomics analysis detected dramatic differences in protein content between newborn and young groups but minor changes among young, adult, and old groups. These results demonstrated: (1) the significant alterations of the enthesis composition and structure occur from the newborn to the young time period; (2) the increased risk of rotator cuff tendon injuries in the elderly population is not solely because of old age alone in the rodent model.

Isolated Partial Intra-Articular Volar Ulnar Fractures of the Distal Radius: The Tetrahedron Variant.

PURPOSE: The aim of this study was to assess the treatment and complications of a distinct type of partial intra-articular distal radius fracture. METHODS: Seven patients treated by the senior author between 2008 and 2013 for a partial intra-articular distal radius fracture with isolated involvement of the volar lunate facet were included. All fragments had the distinctive shape of a triangular-base pyramid (tetrahedron) extending from the metaphysis distally. All fractures were preoperatively assessed with computed tomography (CT) scans. Patients underwent surgical treatment using a standard flexor carpi radialis approach (2 patients) or a volar ulnar approach (5 patients) and were followed postoperatively for a minimum of 12 months. RESULTS: Patient age ranged from 33 to 66 years. On average, fragments measured 34 ± 6 mm in length (range, 27-43 mm) and were 48% as wide as the distal radius (range, 40% to 56%) and 58% as deep as the anterior-posterior dimension of the lesser sigmoid notch (range, 33% to 83%). Loss of reduction requiring revision surgery occurred at 4 weeks in 1 patient who underwent internal fixation through the flexor carpi radialis approach. The remaining cases healed uneventfully. At the final follow-up, all, except the patient requiring revision surgery, had a painless wrist. Average total wrist motion measured 87% of the opposite side. Radiographic healing with anatomic wrist alignment was observed in all except the patient requiring revision. This patient had persistent joint subluxation. The remaining patients all achieved good or excellent functional outcomes. CONCLUSIONS: Isolated tetrahedron volar lunate facet fractures of the distal radius are rare. In our experience, the use of a volar ulnar approach leads to satisfactory fixation and outcomes, yielding excellent radiographic and clinical outcomes. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Locked plating versus cephalomedullary nailing of unstable intertrochanteric femur fractures.

BACKGROUND: Proximal femur locking plates (PFLP) have received increased attention as an alternative for the treatment of proximal femur fractures. However, recent clinical data on these implants has raised concern about higher than expected failure rates. QUESTION/PURPOSE: The purpose of the present study was to compare outcomes of unstable pertrochanteric femur fractures (AO/OTA 31A3) treated at a level-1 trauma center using either PFLP or cephalomedullary nailing (CMN). PATIENTS AND METHODS: Sixty-two patients (31 PFLP and 31 CMN, 55 % female, average age 63 years, range 21-94) with 64 OTA 31A3 fractures (32 PFLP and 32 CMN) treated between 2003 and 2007 were retrospectively reviewed. No differences were found with regard to gender, BMI, diabetes and time to surgery. RESULTS: One patient (5 %) in the CMN group underwent a reoperation (debridement with hardware removal), while eight PFLP patients (25 %) did (two debridements, two hardware removals, four nonunion repairs). One mechanical failure (5 %) occurred in the CMN group and 12 (38 %) in the PFLP group (p = 0.007). One nonunion (5 %) was observed in the CMN group, while 6 (19 %) occurred in the PFLP group. CONCLUSION: A higher rate of reoperation and mechanical failure can be expected for unstable intertrochanteric femur fracture when treated with PFLP than with CMN.

Open surgical release for contractures of the elbow.

Compared with arthroscopic release, open release is more commonly used for the treatment of stiff elbow. Flexion is recovered by releasing posterior tethering soft-tissue structures and by removing anterior impingement between the coronoid and/or radial head and the distal humerus. Extension is improved by releasing anterior soft-tissue tethers and by removing impingement between the olecranon tip and the olecranon fossa. Open elbow release is most commonly performed via ligament-sparing approaches. Ulnar nerve identification and transposition is recommended in the presence of nerve dysfunction or when correction of significant loss of elbow flexion is anticipated. Long-term improvement in flexion and extension can be expected with proper patient selection. Less predictable results are obtained in adolescent patients and in those with underlying traumatic brain injury.

Anterior glenohumeral instability: a pathology-based surgical treatment strategy.

The glenohumeral joint is the most frequently dislocated major joint, and most cases involve an anterior dislocation. Young male athletes competing in contact sports are at especially high risk of recurrent instability. Surgical timing and selection of surgical technique continue to be debated. Full characterization of the injury requires an accurate history and physical examination. Diagnostic imaging assists in identifying the underlying anatomic lesions, which range from no discernible lesion to significant bone loss of the glenoid or humeral head and/or capsulolabral stretching or avulsion from the glenoid or humerus. Historically, open Bankart repair has been considered to be the standard method of managing capsulolabral injuries, but comparable results have been achieved with arthroscopic techniques. In the setting of anterior glenoid bone loss >20% of the articular surface, iliac crest bone grafting or coracoid transfer via the Bristow or Latarjet procedures has demonstrated satisfactory outcomes. Favorable results have been reported with bone grafting or remplissage for engaging Hill-Sachs lesions and those that affect >30% of the humeral circumference.

Low transcondylar fractures of the distal humerus: results of open reduction and internal fixation.

BACKGROUND: This study presents the outcomes of low transcondylar fractures of the distal humerus treated by open reduction and internal fixation. METHODS: Between 1996 and 2010, 263 distal humeral fractures were managed at our institution. Patients with a true low transcondylar fracture treated by open reduction and internal fixation were included. Fourteen patients form the basis of this study. Fracture fixation was achieved through a triceps-sparing approach, a triceps tongue, or an olecranon osteotomy. Internal fixation was performed with parallel plates, orthogonal plates, a single lateral plate, or a single medial plate. The clinical outcome was measured with pain levels, range of motion, and the Mayo Elbow Performance Score. Radiographs at latest follow-up were assessed for union, delayed union, nonunion, and hardware failure. RESULTS: At most recent follow-up, 11 patients had no pain, 2 had mild pain, and 1 had moderate pain. The mean Mayo Elbow Performance Score was 85. The mean arch of motion was 95°. Complications included nonunion, delayed union, wound complications, deep infection, and heterotopic ossification. DISCUSSION: Stable internal fixation of low transcondylar fractures is perceived as difficult to achieve because of the very small size of the distal fragment. However, the results of our study indicate that internal fixation of low transcondylar fractures of the distal humerus is associated with a high union rate and satisfactory clinical results. Elbow arthroplasty does not need to be considered for most patients with a low transcondylar distal humeral fracture.

Mortality after periprosthetic femur fractures.

Periprosthetic femur fractures are becoming more frequent, as the prevalence of hip and knee arthroplasties keeps increasing and our population continues to age. Although the vast majority of literature on periprosthetic fractures has centered on radiographic and functional outcomes, only limited information is available on mortality. Patients with periprosthetic femur fractures are at a similar or higher mortality risk than hip fracture patients. Furthermore, periprosthetic femur fractures carry a significantly higher mortality risk than hip or knee arthroplasty or operative fixation of native distal femur fractures. Advanced patient age and underlying comorbidities increase the risk of mortality. Factors related to the injury itself and treatment method may play an additional role, especially during the short postoperative period.

Use of negative-pressure wound therapy in orthopaedic trauma.

Negative-pressure wound therapy (NPWT) has become an important adjunct to the management of traumatic wounds and surgical incisions related to musculoskeletal trauma. On the battlefield, this adjunct therapy allows early wound management and safe aeromedical evacuation. NPWT mechanisms of action include stabilization of the wound environment, reduction of wound edema, improvement of tissue perfusion, and stimulation of cells at the wound surface. NPWT stimulates granulation tissue and angiogenesis and may improve the likelihood of primary closure and reduce the need for free tissue transfer. In addition, NPWT reduces the bacterial bioburden of wounds contaminated with gram-negative bacilli. However, an increased risk of colonization of gram-positive cocci (eg, Staphylococcus aureus) exists. Although NPWT facilitates wound management, further research is required to determine conclusively whether this modality is superior to other management options. Ongoing research will continue to define the indications for and benefits of NPWT as well as establish the role of combination therapy, in which NPWT is used with instillation of antibiotic solutions, placement of antibiotic-laden cement beads, or silver-impregnated sponges.

Outcomes of Orthopaedic Infections in Recreational Intravenous Drug Users Requiring Long-term Antibiotic Treatment.

Patients who participate in recreational injection drug use (RIVDU) have an increased risk of orthopaedic infections requiring prolonged treatment with intravenous antibiotics. This study reviews clinical outcomes and complications in RIVDU and have orthopaedic infections requiring long term antibiotic therapy (>4 weeks) and compares these outcomes to non-RIVDU patients. In this retrospective review, patients were divided into cohorts based on RIVDU history; the RIVDU cohort was further divided into subcohorts based on treatment location. Cohorts and subcohorts were compared to evaluate clinical outcomes. Between the two main cohorts, there was a statistically significant difference in treatment compliance (P = 0.0012) and no statistically significant differences for infection resolution at 6- or 12-month follow-up, hospital readmission, or mortality. At the 6-month follow-up, RIVDU patients who remained inpatient had 100% resolution of infection, which was significantly better than the resolution of all other cohorts (P = 0.0019). No differences were observed between the remaining subcohorts for resolution of infection by 12 months, catheter complications, or loss to follow-up. Our findings demonstrate an increased rate of failure in outpatient parenteral antibiotic therapy in RIVDU patients, and this population has better clinical outcomes when they remain inpatient for the duration of treatment.

Mortality after distal femur fractures in elderly patients.

BACKGROUND: Hip fractures in the elderly are associated with high 1-year mortality rates, but whether patients with other lower extremity fractures are exposed to a similar mortality risk is not clear. QUESTIONS/PURPOSES: We evaluated the mortality of elderly patients after distal femur fractures; determined predictors for mortality; analyzed the effect of surgical delay; and compared survivorship of elderly patients with distal femur fractures with subjects in a matched hip fracture group. PATIENTS AND METHODS: We included 92 consecutive patients older than 60 years with low-energy supracondylar femur fractures treated between 1999 and 2009. Patient, fracture, and treatment characteristics were extracted from operative records, charts, and radiographs. Data regarding mortality were obtained from the Social Security Death Index. RESULTS: Age-adjusted Charlson Comorbidity Index and a previous TKA were independent predictors for decreased survival. Congestive heart failure, dementia, renal disease, and history of malignant tumor led to shorter survival times. Patients who underwent surgery more than 4 days versus 48 hours after admission had greater 6-month and 1-year mortality risks. No differences in mortality were found comparing patients with native distal femur fractures with patients in a hip fracture control group. CONCLUSIONS: Periprosthetic fractures and fractures in patients with dementia, heart failure, advanced renal disease, and metastasis lead to reduced survival. The age-adjusted Charlson Comorbidity Index may serve as a useful tool to predict survival after distal femur fractures. Surgical delay greater than 4 days increases the 6-month and 1-year mortality risks. Mortality after native fractures of the distal femur in the geriatric population is high and similar to mortality after hip fractures. LEVEL OF EVIDENCE: Level II, prognostic study. See the guidelines online for a complete description of evidence.

Differential fracture healing resulting from fixation stiffness variability: a mouse model.

BACKGROUND: The mechanisms underlying the interaction between the local mechanical environment and fracture healing are not known. We developed a mouse femoral fracture model with implants of different stiffness, and hypothesized that differential fracture healing would result. METHODS: Femoral shaft fractures were created in 70 mice, and were treated with an intramedullary nail made of either tungsten (Young's modulus = 410 GPa) or aluminium (Young's modulus = 70 GPa). Mice were then sacrificed at 2 or 5 weeks. Fracture calluses were analyzed using standard microCT, histological, and biomechanical methods. RESULTS: At 2 weeks, callus volume was significantly greater in the aluminium group than in the tungsten group (61.2 vs. 40.5 mm(3), p = 0.016), yet bone volume within the calluses was no different between the groups (13.2 vs. 12.3 mm(3)). Calluses from the tungsten group were stiffer on mechanical testing (18.7 vs. 9.7 N/mm, p = 0.01). The percent cartilage in the callus was 31.6% in the aluminium group and 22.9% in the tungsten group (p = 0.40). At 5 weeks, there were no differences between any of the healed femora. CONCLUSIONS: In this study, fracture implants of different stiffness led to different fracture healing in this mouse fracture model. Fractures treated with a stiffer implant had more advanced healing at 2 weeks, but still healed by callus formation. Although this concept has been well documented previously, this particular model could be a valuable research tool to study the healing consequences of altered fixation stiffness, which may provide insight into the pathogenesis and ideal treatment of fractures and non-unions.

Surgeon practices regarding operative treatment of posterior malleolus fractures.

BACKGROUND: Operative indications for surgical treatment of posterior malleolar fractures associated with fractures of the distal fibula and tibia are not currently well defined. The purpose of the present study was to determine the current practice among orthopaedic surgeons regarding the management of posterior malleolus fractures. MATERIALS AND METHODS: Web-based questionnaires were emailed to members of the Orthopaedic Trauma Association (OTA) and American Orthopaedic Foot and Ankle Society (AOFAS). Requested information included demographics and treatment preferences for five clinical scenarios with different fracture characteristics. Four hundred one respondents completed the survey (20% response rate). Ninety eight (24%) subjects had received specialty training in orthopaedic trauma, 199 (50%) in foot and ankle (F&A) surgery and six (2%) in both orthopaedic trauma and F&A surgery. Ninety five (24%) had either no or other specialty training. RESULTS: The most frequently reported indication for fixation was not based on a fragment size threshold, but rather was ``depends on stability and other factors'' (56%). Trauma surgeons, those with less than 10 years experience, and those who treated more than five ankles fractures per month were significantly more likely to use factors other than size for indications (p = 0.026, <0.01, and <0.01, respectively). Despite this general response, fragment size still affected treatment decisions. A fragment comprising 50% of the articular surface was indicated for fixation by 97% of respondents, while a size of 10% would be treated by only 9% of respondents. For a posterior fragment with 20% articular involvement and a small free osteochondral fragment, fixation was deemed necessary by 44% of respondents. There were no differences in fellowship training, years of experience in practice, or ankle fracture volume per month in these three situations. A larger proportion of trauma trained surgeons considered fixation necessary compared to F&A trained surgeons in this case (p = 0.028). When posterior malleolus fixation was indicated for a large fragment, direct open reduction using the flexor hallucis longus -peroneal tendon interval was the most commonly selected approach in all cases. Trauma-trained surgeons were significantly more likely to choose antiglide plate fixation compared to screw-only fixation (p < 0.05). CONCLUSION: In this survey study of trauma and F&A surgeons, significant variation existed regarding most aspects of posterior malleolar ankle fracture treatment. Most notably, factors other than fragment size most impacted surgical indications. Newer techniques such as direct exposure and plating of the posterior malleolus are chosen more frequently than traditional techniques of indirect reduction and percutaneous screw fixation.

Minimally invasive plate osteosynthesis for humeral shaft fractures: are results reproducible?

Minimally invasive plate osteosynthesis (MIPO) has been advocated as a safe approach to humeral shaft fracture management. We evaluated the reproducibility of this technique in a regional hospital. Thirty-five patients underwent MIPO of humerus shaft fractures. Fifteen patients had an open fracture, six a preoperative radial nerve palsy, and nine a concomitant thoracic, musculoskeletal or vascular injury. At an average 12-month follow-up, 91% of fractures healed after a mean of 12 weeks (range, 8-16). Two infections occurred. Final alignment averaged 4° of varus (range, 5° of valgus to 20° of varus). Active elbow ROM averaged 114° (range, 60-135°) and was less than 100° in nine elbows. Five of six preoperative radial nerve injuries recovered spontaneously. Healing and infection rates in this study are consistent with those reported in the literature. Lower elbow ROM and higher fracture angulation at healing were nevertheless found. MIPO is technically demanding and requires adequate intraoperative imaging and surgical experience in order to obtain adequate fracture alignment. Brachialis muscle scarring and inadequate postoperative rehabilitation may be involved in limited elbow range of motion.

Electrospun thymosin Beta-4 loaded PLGA/PLA nanofiber/ microfiber hybrid yarns for tendon tissue engineering application.

Microfiber yarns (MY) have been widely employed to construct tendon tissue grafts. However, suboptimal ultrastructure and inappropriate environments for cell interactions limit their clinical application. Herein, we designed a modified electrospinning device to coat poly(lactic-co-glycolic acid) PLGA nanofibers onto polylactic acid (PLA) MY to generate PLGA/PLA hybrid yarns (HY), which had a well-aligned nanofibrous structure, resembling the ultrastructure of native tendon tissues and showed enhanced failure load compared to PLA MY. PLGA/PLA HY significantly improved the growth, proliferation, and tendon-specific gene expressions of human adipose derived mesenchymal stem cells (HADMSC) compared to PLA MY. Moreover, thymosin beta-4 (Tß4) loaded PLGA/PLA HY presented a sustained drug release manner for 28 days and showed an additive effect on promoting HADMSC migration, proliferation, and tenogenic differentiation. Collectively, the combination of Tß4 with the nano-topography of PLGA/PLA HY might be an efficient strategy to promote tenogenesis of adult stem cells for tendon tissue engineering.

3D printing of multilayered scaffolds for rotator cuff tendon regeneration.

Repairing massive rotator cuff tendon defects remains a challenge due to the high retear rate after surgical intervention. 3D printing has emerged as a promising technique that enables the fabrication of engineered tissues with heterogeneous structures and mechanical properties, as well as controllable microenvironments for tendon regeneration. In this study, we developed a new strategy for rotator cuff tendon repair by combining a 3D printed scaffold of polylactic-co-glycolic acid (PLGA) with cell-laden collagen-fibrin hydrogels. We designed and fabricated two types of scaffolds: one featuring a separate layer-by-layer structure and another with a tri-layered structure as a whole. Uniaxial tensile tests showed that both types of scaffolds had improved mechanical properties compared to single-layered PLGA scaffolds. The printed scaffold with collagen-fibrin hydrogels effectively supported the growth, proliferation, and tenogenic differentiation of human adipose-derived mesenchymal stem cells. Subcutaneous implantation of the multilayered scaffolds demonstrated their excellent in vivo biocompatibility. This study demonstrates the feasibility of 3D printing multilayered scaffolds for application in rotator cuff tendon regeneration.

Fingerbreadths Rule in Determining the Safe Zone of the Radial Nerve and Posterior Interosseous Nerve for a Lateral Elbow Approach: An Anatomic Study.

INTRODUCTION: The purpose of this study was to investigate whether a safe zone rule could be applied to prevent iatrogenic injuries to the radial nerve (RN); and determine whether there is a relationship between the diameter of the radial head and capitellum and the distance of the posterior interosseous nerve (PIN) to the radiocapitellar joint. METHODS: Ten fresh-frozen cadaveric specimens were used to measure the distances between the RN and the lateral epicondyle; the PIN and the radiocapitellar joint; the lateral epicondyle and the PIN as it crossed the ulnohumeral joint; the diameter of the radial head; the width of the capitellum; and the fingerbreadths of the specimens. RESULTS: Four fingerbreadths determined a safe zone between the lateral epicondyle and the RN proximally at the point at which it pierced the intermuscular septum and the mid-lateral portion of the humeral shaft. Two fingerbreadths provided a safe zone for the PIN from the radiocapitellar joint to the midpoint of the axis of the radius only with the forearm in pronation. CONCLUSION: A four-finger rule, two-finger rule, and radial head diameter or capitellum size may predict a safe zone for the RN and PIN except for the segment of the nerve where it crosses the anterior cortex of either the humerus or radius. LEVEL OF EVIDENCE: Preclinical cadaveric study.

Living nanofiber yarn-based woven biotextiles for tendon tissue engineering using cell tri-culture and mechanical stimulation.

Non-woven nanofibrous scaffolds have been developed for tendon graft application by using electrospinning strategies. However, electrospun nanofibrous scaffolds face some obstacles and limitations, including suboptimal scaffold structure, weak tensile and suture-retention strengths, and compact structure for cell infiltration. In this work, a novel nanofibrous, woven biotextile, fabricated based on electrospun nanofiber yarns, was implemented as a tissue engineered tendon scaffold. Based on our modified electrospinning setup, polycaprolactone (PCL) nanofiber yarns were fabricated with reproducible quality, and were further processed into plain-weaving fabrics interlaced with polylactic acid (PLA) multifilaments. Nonwoven nanofibrous PCL meshes with random or aligned fiber structures were generated using typical electrospinning as comparative counterparts. The woven fabrics contained 3D aligned microstructures with significantly larger pore size and obviously enhanced tensile mechanical properties than their nonwoven counterparts. The biological results revealed that cell proliferation and infiltration, along with the expression of tendon-specific genes by human adipose derived mesenchymal stem cells (HADMSC) and human tenocytes (HT), were significantly enhanced on the woven fabrics compared with those on randomly-oriented or aligned nanofiber meshes. Co-cultures of HADMSC with HT or human umbilical vein endothelial cells (HUVEC) on woven fabrics significantly upregulated the functional expression of most tenogenic markers. HADMSC/HT/HUVEC tri-culture on woven fabrics showed the highest upregulation of most tendon-associated markers than all the other mono- and co-culture groups. Furthermore, we conditioned the tri-cultured constructs with dynamic conditioning and demonstrated that dynamic stretch promoted total collagen secretion and tenogenic differentiation. Our nanofiber yarn-based biotextiles have significant potential to be used as engineered scaffolds to synergize the multiple cell interaction and mechanical stimulation for promoting tendon regeneration. STATEMENT OF SIGNIFICANCE: Tendon grafts are essential for the treatment of various tendon-related conditions due to the inherently poor healing capacity of native tendon tissues. In this study, we combined electrospun nanofiber yarns with textile manufacturing strategies to fabricate nanofibrous woven biotextiles with hierarchical features, aligned fibrous topography, and sufficient mechanical properties as tendon tissue engineered scaffolds. Comparing to traditional electrospun random or aligned meshes, our novel nanofibrous woven fabrics possess strong tensile and suture-retention strengths and larger pore size. We also demonstrated that the incorporation of tendon cells and vascular cells promoted the tenogenic differentiation of the engineered tendon constructs, especially under dynamic stretch. This study not only presents a novel tissue engineered tendon scaffold fabrication technique but also provides a useful strategy to promote tendon differentiation and regeneration.

Total Elbow Arthroplasty for Distal Humeral Fractures: A Ten-Year-Minimum Follow-up Study.

BACKGROUND: Total elbow arthroplasty is commonly considered for elderly patients with comminuted distal humeral fractures. Satisfactory short-term outcomes have been reported, but long-term outcomes are unknown. Our purpose was to assess the long-term outcomes of total elbow arthroplasty after distal humeral fracture and to determine differences between elbows with or without inflammatory arthritis at the time of fracture. METHODS: Forty-four total elbow arthroplasties were performed after distal humeral fracture; those patients were followed for a minimum of 10 years and were evaluated with regard to pain, motion, Mayo Elbow Performance Scores, complications, and reoperations. The outcomes in elbows with and without inflammatory arthritis were compared. Kaplan-Meier survivorship analysis was performed. RESULTS: Total elbow arthroplasty provided good pain relief and motion; the mean visual analog scale for pain was 0.6, the mean flexion was 123°, and the mean loss of extension was 24°. The mean Mayo Elbow Performance Score was 90.5 points, with 3 patients scoring <75 points. Five elbows (11%) developed deep infection, treated surgically with component retention (3 acute) or resection (2 chronic). Implant revision or resection was performed in 8 elbows (18%): 3 for infections (1 reimplantation and 2 resections), 3 for ulnar loosening (associated with periprosthetic fracture in 1), and 2 for ulnar component fractures. Additional periprosthetic fractures were observed in 5 elbows. The survival rates for elbows with rheumatoid arthritis were 85% at 5 years and 76% at 10 years, and the survival rates for elbows without rheumatoid arthritis were 92% at both 5 and 10 years. The most relevant risk factor for revision was male sex (hazard ratio, 12.6 [95% confidence interval, 1.7 to 93.6]). CONCLUSIONS: Selective use of total elbow arthroplasty to treat fractures of the distal part of the humerus for infirm, less active older patients and patients with inflammatory arthritis has acceptable longevity in surviving patients, but at the cost of a number of major complications. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effects of Hydroxyapatite and Hypoxia on Chondrogenesis and Hypertrophy in 3D Bioprinted ADMSC Laden Constructs.

Hydrogel-based cartilage tissue engineering strategies require the induction and long-term maintenance of adipose derived mesenchymal stem cells (ADMSC) into a stable chondrogenic phenotype. However, ADMSC exhibit the tendency to undergo hypertrophic differentiation, rather than forming permanent hyaline cartilage phenotype changes. This may hinder their implementation in articular cartilage regeneration, but may allow the possibility for bone and bone to soft tissue interface repair. In this study, we examined the effects of hydroxyapatite (HAp) on the chondrogenesis and hypertrophy of ADMSC within bioprinted hyaluronic acid (HA)-based hydrogels. We found that a small amount of HAp (∼10% of polymer concentration) promoted both chondrogenic and hypertrophic differentiation of ADMSC. Increased HAp contents promoted hypertrophic conversion and early osteogenic differentiation of encapsulated ADMSC. Subsequently, ADMSC-laden, stratified constructs with nonmineralized and mineralized layers (i.e., HA based and HA-HAp based) were 3D bioprinted. The constructs were conditioned in chondrogenic medium in either a normoxic or hypoxic environment for 8 weeks to assess the effects of oxygen tension on ADMSC differentiation and interface integration. We further implanted the bioprinted constructs subcutaneously into nude mice for 4 weeks. It was found that hypoxia partially inhibited hypertrophic differentiation by significantly down-regulating the expression of COL10A1, ALP, and MMP13. In addition, hypoxia also suppressed spontaneous calcification of ADMSC and promoted interface integration. This study demonstrates that both HAp content and hypoxia are important to mediate chondrogenesis, hypertrophy, and endochondral ossification of ADMSC. An optimized recipe and condition will allow for 3D bioprinting of multizonal grafts with integrated hard tissue and soft tissue interfaces for the treatment of complex orthopedic defects.

Effect of scaffold morphology and cell co-culture on tenogenic differentiation of HADMSC on centrifugal melt electrospun poly (L­lactic acid) fibrous meshes.

Engineered tendon grafts offer a promising alternative for grafting during the reconstruction of complex tendon tears. The tissue-engineered tendon substitutes have the advantage of increased biosafety and the option to customize their biochemical and biophysical properties to promote tendon regeneration. In this study, we developed a novel centrifugal melt electrospinning (CME) technique, with the goal of optimizing the fabrication parameters to generate fibrous scaffolds for tendon tissue engineering. The effects of CME processing parameters, including rotational speed, voltage, and temperature, on fiber properties (i.e. orientation, mean diameter, and productivity) were systematically investigated. By using this solvent-free and environmentally friendly method, we fabricated both random and aligned poly (L-lactic acid) (PLLA) fibrous scaffolds with controllable mesh thickness. We also investigated and compared their morphology, surface hydrophilicity, and mechanical properties. We seeded human adipose derived mesenchymal stem cells (HADMSC) on various PLLA fibrous scaffolds and conditioned the constructs in tenogenic differentiation medium for up to 21 days, to investigate the effects of fiber alignment and scaffold thickness on cell behavior. Aligned fibrous scaffolds induced cell elongation and orientation through a contact guidance phenomenon and promoted HADMSC proliferation and differentiation towards tenocytes. At the early stage, thinner scaffolds were beneficial for HADMSC proliferation, but the scaffold thickness had no significant effects on cell proliferation for longer-term cell culture. We further co-seeded HADMSC and human umbilical vein endothelial cells (HUVEC) on aligned PLLA fibrous mats and determined how the vascularization affected HADMSC tenogenesis. We found that co-cultured HADMSC-HUVEC expressed more tendon-related markers on the aligned fibrous scaffold. The co-culture systems promoted in vitro HADMSC differentiation towards tenocytes. These aligned fibrous scaffolds fabricated by CME technique could potentially be utilized to repair and regenerate tendon defects and injuries with cell co-culture and controlled vascularization.