The impact of asymptomatic human immunodeficiency virus (HIV)-positive disease status on inpatient complications following total joint arthroplasty: a propensity score-matched analysis.

PURPOSE: The number of patients with asymptomatic human immunodeficiency virus (AHIV) is increasing as the efficacy of antiretroviral therapy improves. While there is research on operative risks associated with having HIV, there is a lack of literature describing the impact of well-controlled HIV on postoperative complications. This study seeks to elucidate the impact of AHIV on postoperative outcomes after total hip (THA) and knee (TKA) arthroplasty. METHODS: The Nationwide Inpatient Sample was retrospectively reviewed for patients undergoing TKA and THA from 2005 to 2013. Subjects were subdivided into those with AHIV and those without HIV (non-HIV). Patient demographics, hospital-related parameters, and postoperative complications were all collected. One-to-one propensity score-matching, Chi-square analysis, and multivariate logistical regressions were performed to compare both cohorts. RESULTS: There were no significant differences between AHIV and non-HIV patients undergoing TKA or THA in terms of sex, age, insurance status, or total costs (all, p ≥ 0.081). AHIV patients had longer lengths of stay (4.0 days) than non-HIV patients after both TKA (3.3 days) and THA (3.1 days) (p ≤ 0.011). Both TKA groups had similar postoperative complication rates (p > 0.081). AHIV patients undergoing THA exhibited an increased rate of overall surgical complications compared non-HIV patients (0 vs. 4.5%, p = 0.043). AHIV was not associated with increased complications following both procedures. CONCLUSION: Despite lengthier hospital stays among AHIV patients, baseline AHIV was not associated with adverse outcomes following TKA and THA. This adds to the literature and warrants further research into the impact of asymptomatic, well-controlled HIV infection on postoperative outcomes following total joint arthroplasty.

Temporary new implant spacers increase post-reimplantation total knee prosthesis survival after periprosthetic joint infection.

PURPOSE: Two-stage exchange arthroplasty is considered the gold standard for treatment of periprosthetic joint infection (PJI) following total knee arthroplasty (TKA). Antibiotic cement spacers can include cement-based spacers (CBS), new components (NEW), and autoclaved components (ACL). The factors that most influence post-reimplantation prosthesis (PRP) survival were determined. METHODS: A retrospective database review of patients undergoing two-stage exchange arthroplasty from 2008 to 2014 was performed. There were 85 patients, 25 patients and 30 patients in CBS, NEW and ACL groups, respectively. Patient, disease and surgical characteristics were collected and analyzed. Post-reimplantation prosthesis (PRP) survival was modeled using the Kaplan-Meier method. Cox proportional hazard modeling was then performed to identify risk factors associated with implant failure. RESULTS: Overall PRP survival was 82% in 140 unilateral TKAs. PRP survival between groups was 81%, 96% and 73% within the minimum 2-year follow-up period, respectively. There was a difference in median interval-to-reimplantation between groups (CBS, 72.0 days; NEW, 111.0 days; ACL, 84.0 days, p = 0.003). Adjusting for time-to-reimplantation, NEW spacers demonstrated greater PRP survival compared with ACL spacers (p = 0.044), and a trend towards greater survival compared with CBS spacers (p = 0.086). Excluding early failures (< 90 days), NEW spacers still demonstrated greater survival than ACL spacers (p = 0.046). Lower volume (≤ 10 within this series) surgeons tended to use more CBS spacers, while higher volume surgeons were comfortable with ACL spacers. CONCLUSIONS: There was greater PRP survival with NEW spacers. NEW spacers also demonstrated an increased inter-stage interval, likely because of increased comfort and motion. There were spacer choice differences between low- and high-volume surgeons. LEVEL OF EVIDENCE: III.

Taper Design, Head Material, and Manufacturer Affect the Onset of Fretting Under Simulated Corrosion Conditions.

BACKGROUND: We investigated the effect of taper design, head material, and manufacturer on simulated mechanically assisted crevice corrosion (MACC). METHODS: Six pristine C-taper stems coupled with alumina-zirconia or cobalt-chromium (CoCr) heads were tested in a mechanical/electrochemical setup to measure average fretting currents and fretting current onset loads. Outcomes were compared with previous data from V40 tapers from the same manufacturer and 12/14 tapers from another manufacturer. RESULTS: Within a single manufacturer, differences in average fretting current between V40 and C-taper designs were dependent on head material. Only with V40 tapers did CoCr heads show higher average fretting currents than ceramic heads. Between manufacturers, differences were found between similar taper designs, as 12/14 taper couples showed higher average fretting currents than C-taper couples, regardless of head material. CONCLUSION: Taper design, head material, and factors inherent to different manufacturers influence fretting current in simulated MACC. Unlike clinical and retrieval studies, this experimental design allows for investigations of factors affecting MACC in a controlled environment. Taper design, independent of manufacturer, contributes to the observed differences in average fretting current between head materials. In some taper designs, head composition, specifically ceramic, should not be considered alone to reduce risk of corrosion.

Using Imageless Optical Navigation to Identify the New Hip Center in Crowe IV Dysplasia.

In total hip arthroplasty for patients with acetabular dysplasia, cup placement in the native acetabulum is preferred to placement in the pseudoacetabulum. Identifying the true acetabulum may prove challenging. In a patient with Crowe IV dysplasia, 3-dimensional mini-optical navigation was used to match the new hip center to the preoperative radiographic plan, which was identified to be 34 mm inferior to the pseudoacetabulum. This allowed titration of femoral shortening to 20 mm, to arrive at final limb lengthening of 14 mm. Although the use of other enabling technologies in hip dysplasia has been reported, to the authors' knowledge, this is the first reported case demonstrating the use of imageless optical navigation in this setting. It is a navigational tool with a small spatial footprint, does not mandate preoperative axial studies, and does not require multipoint bone surface registration. Imageless navigation may be a useful option for cup positioning and subsequent titration of femoral shortening in the reconstruction of Crowe IV dysplastic hips with degenerative joint disease. [Orthopedics. 2020; 43(2):e119-e122.].

In Hospital Outcomes of Total Hip Arthroplasty in the Medicaid Population.

Total hip arthroplasty (THA) is one of the most common orthopaedic procedures. This study's purpose was to evaluate national trends, patient demographics and hospital outcomes for Medicaid patients who underwent a primary THA. The National Hospital Discharge Survey (NHDS) database was queried for patients undergoing THA from 2001-2010. Patients were stratified into two groups based on insurance. We found from 2001-2005, Medicaid accounted for 2.38% of all THA performed, increasing insignificantly to 2.61% between 2006-2010. The Medicaid group was younger (50.3 vs. 65.6 years, p < 0.01). Length of stay was longer for the Medicaid group (4.6 vs. 4.0 days, p < 0.01). Medicaid patients were more likely to be discharged home (53.7% vs. 47.2%, p < 0.01) and less likely to be discharged to rehabilitation facilities (24.4% vs. 29.0%, p < 0.05). In conclusion, we discovered that the rate of Medicaid insurance in patients undergoing primary THA was stable through 2010, prior to the Affordable Care Act. We found Medicaid THA patients had longer length of stay, despite being a mean 15 years younger than the non-Medicaid cohort. Medicaid insurance status should be factored into risk adjustment models to avoid creating additional disincentive to treat the Medicaid population. (Journal of Surgical Orthopaedic Advances 28(4):281-284, 2019).

Dynamic sensor-balanced knee arthroplasty: can the sensor "train" the surgeon?

BACKGROUND: Dynamic tibial tray sensors are playing an increasing role in total knee arthroplasty (TKA) coronal balancing. Sensor balance is proposed to lead to improved patient outcomes compared with sensor-unbalanced TKA, and traditional manual-balanced TKA. However, the "learning curve" of this technology is not known, and also whether sensor use can improve manual TKA balance skills once the sensor is taken away, effectively "training" the surgeon. METHODS: We conducted a single-surgeon prospective study on 104 consecutive TKAs. In Nonblinded Phase I (n = 49), sensor-directed releases were performed during trialing and final intercompartmental load was recorded. In Blinded Phase II (n = 55), manual-balanced TKA was performed and final sensor readings were recorded by a blinded observer after cementation. We used cumulative summation analysis and sequential probability ratio testing to analyze the surgeon learning curve in both phases. RESULTS: In Nonblinded Phase I, sensor balance proficiency was attained most easily at 10°, followed by 90°, and most difficult to attain at 45° of flexion. In Blinded Phase II, manual balance was lost most quickly at 45°, followed by 90°, and preserved for longest at 10° of flexion. The number of cases in the steady state periods (early phase periods where there is a mix of sensor balance and sensor imbalance) for both phases is similar. CONCLUSIONS: A surgeon who consistently uses the dynamic sensor demonstrates a learning curve with its use, and an "attrition" curve once it is removed. Consistent sensor balance is more predictable with constant sensor use.

Aspirin Alone Is Not Enough to Prevent Deep Venous Thrombosis After Total Joint Arthroplasty.

Thromboembolic events after total joint arthroplasty are potentially devastating complications. This study evaluated the efficacy of 4 different anticoagulants in preventing deep venous thrombosis and pulmonary embolism after total joint arthroplasty. The demographics and anticoagulant use (warfarin, enoxaparin, and aspirin with and without outpatient mechanical pumps) for patients who underwent primary unilateral total joint arthroplasties performed by a single surgeon from January 2013 to October 2014 were retrospectively reviewed. All patients underwent lower extremity ultrasound at the 3-week postoperative visit. A total of 613 primary unilateral total joint arthroplasties met the study inclusion criteria. There were 288 primary total knee arthroplasties and 325 primary total hip arthroplasties. The patients were 62.2% female, having a mean age of 67.6±10.6 years and a mean body mass index of 30.2±5.9 kg/m2. There were 119 patients in group 1 (aspirin alone), 40 patients in group 2 (aspirin plus pumps), 246 patients in group 3 (warfarin), and 208 patients in group 4 (enoxaparin). The overall 3-week symptomatic and asymptomatic deep venous thrombosis and symptomatic pulmonary embolism rates in the entire cohort were 5.7% and 0.3%, respectively. The venous thromboembolism rate was significantly affected by the anticoagulant of choice (P<.01). Compared with aspirin alone, warfarin decreased the risk of venous thromboembolism (P<.01). Increasing age led to increased risk of venous thromboembolism (P=.05). This study indicated that aspirin chemoprophylaxis alone was not as efficacious as warfarin and enoxaparin in preventing asymptomatic and symptomatic venous thromboembolism found during routine postoperative surveillance with lower extremity ultrasound. Aspirin alone may be inadequate and should be augmented with an outpatient mechanical pump as part of multimodal prophylaxis. [Orthopedics. 2019; 42(1):48-55.].

Return to the operating room after patellofemoral arthroplasty versus total knee arthroplasty for isolated patellofemoral arthritis-a systematic review.

PURPOSE: Patellofemoral arthroplasty (PFA) and total knee arthroplasty (TKA) are accepted treatments for end-stage isolated patellofemoral osteoarthritis (PFOA). However, complications and re-operations have historically differed between the two procedures. We performed a systematic review to report on the re-operation rates between TKA and modern PFA for isolated PFOA. METHODS: Systematically identified publications reporting on patients that underwent either TKA or modern PFA for isolated PFOA were reviewed. Meta-analysis software was used to screen potential articles with at least one year follow-up that detailed reasons for re-operation. Data was extracted and analyzed for all re-operations. Survival of the implant was used as the primary outcome; return to the operating room (OR) for any reason was used as a secondary outcome. RESULTS: The weighted rate of either conversion or revision arthroplasty in the PFA group and the TKA group was 6.34 and 0.11, respectively. The weighted rate of return to the OR for bony and soft tissue procedures was 1.06 and 0.79, respectively. The weighted rate of manipulation under anaesthesia (MUA) was 0.32 and 1.23, respectively. CONCLUSION: Patients who undergo PFA may be more likely to return to the operating room for conversion to TKA and/or revision surgery than those who undergo TKA.

Extreme proximal junctional kyphosis-a complication of delayed lambdoid suture closure in Hajdu-Cheney syndrome: a case report and literature review.

PURPOSE: To describe the manifestations, surgical treatment, and potential complications of Hajdu-Cheney syndrome (HCS), and the management of these complications. METHODS: The clinical presentation, management and outcome of HCS with severe osteoporosis and open skull sutures is presented, together with a literature review. RESULTS: A 20-year-old female with HCS underwent posterior occipitocervical fusion for symptoms of progressive basilar invagination. Because of delayed lambdoid suture closure, the stiff fusion construct lead to increased suture distraction, most notably in the upright (suture-open) position, with relief in the supine (suture-closed) position. This was successfully remedied with extension of the fusion construct anteriorly over the skull vertex to the frontal bones. CONCLUSIONS: In patients with HCS and other conditions with delayed suture closure, the surgeon must be cognizant of the presence of mobility at the suture lines, and consider extending the fusion construct anteriorly over the skull vertex up to the frontal bones. Because of significant osteoporosis in these syndromes, multiple fixation points and augmentation with bone graft are important principles.

A Stepwise Approach to Management of Open Radiocarpal Fracture-Dislocations: A Case Report.

Radiocarpal dislocations are uncommon and occur after significant trauma. We describe a unique case of open radiocarpal fracture-dislocation presenting with progressive neurovascular compromise. Staged management was necessary. As a first stage, emergent provisional bedside reduction in the emergency room with manual pressure through the open wounds was performed. The second stage then involved formal open reduction and internal fixation as soon as operating room staff and resources became available.

That Tendon is the Median Nerve: Perils of a Palmaris Longus Deficient Wrist.

BACKGROUND: To document the course of the median nerve in the distal forearm in palmaris longus (PL) deficient forearms and elucidate features that help distinguish it from the PL. METHODS: In the cadaveric study, 56 cadaveric forearms were dissected and the location and course of the median nerve were documented. In the clinical study, 20 healthy subjects with absent PL were examined with provocative tests to elucidate the PL (Schaeffer's test and Thompson's test), and modified Durkan's and Phalen's tests. In the imaging study, one subject with a clearly visible and palpable median nerve was further evaluated with MRI with a superficial fiducial marker. RESULTS: Cadaveric dissection revealed that the median nerve was deep to the antebrachial fascia and superficial to the FDS tendons in the distal forearm. In 9 specimens without a PL, the median nerve was the most superficial structure deep and lay draped over the FDS tendons. In the clinical study, PL absence was bilateral in 4 subjects and unilateral in 16. The nerve was visible and palpable in 4 forearms and palpable but not visible in 20 forearms. In all 24 forearms, the nerve was palpable as a lax, mobile, cord-like structure that could be rolled over the taut FDS tendons. Tinel's and Durkan's signs were positive in 11 subjects. In the imaging study, MRI confirmed that the palpable structure was the median nerve. CONCLUSIONS: Unlike the PL, the nerve is non-contractile and remains flaccid on provocative testing. It is usually palpable and may also be visible in thin forearms. Careful scrutiny may reveal it to be distinct from, and draped over underlying FDS tendons. These findings may help avoid inadvertent median nerve harvest in place of a PL tendon graft.

Optimized Repopulation of Tendon Hydrogel: Synergistic Effects of Growth Factor Combinations and Adipose-Derived Stem Cells.

Background: Tendon-derived extracellular matrix (ECM) hydrogel has been shown to augment tendon healing in vivo. We hypothesized that reseeding of the gel with adipose-derived stem cells (ASCs) could further assist repopulation of the gel and that combinations of growth factors (GFs) would improve the survival of these cells after reseeding. Methods: A tendon-specific ECM solution was supplemented with varying concentrations of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), and platelet-derived growth factor-BB (PDGF-BB). Gels were then seeded with ASCs transfected with a green fluorescent protein/luciferin construct. Cell proliferation was determined using the MTT assay and histology, and GF and ASC augmented gels were injected into the back of Sprague Dawley rats. Bioluminescence of seeded gels was continuously followed after reseeding, and cell counts were performed after the gels were explanted at 14 days. Results: Synergistic effects of the GFs were seen, and an optimal combination was determined to be 10 ng/mL bFGF, 100 ng/mL IGF-1, and 100 ng/mL PDGF-BB (2.8-fold increase; P < .05). In vivo bioluminescence showed an improved initial survival of cells in gels supplemented with the optimal concentration of GF compared with the control group (10.6-fold increase at 8 days; P < .05). Cell counts of explants showed a dramatic endogenous repopulation of gels supplemented by GF + ASCs compared with both gels with GF but no ASCs (7.6-fold increase) and gels with ASCs but no GF (1.6-fold increase). Conclusion: Synergistic effects of GFs can be used to improve cellular proliferation of ASCs seeded to a tendon ECM gel. Reseeding with ASCs stimulates endogenous repopulation of the gel in vivo and may be used to further augment tendon healing.

Total Hip Arthroplasty and Hemiarthroplasty: US National Trends in the Treatment of Femoral Neck Fractures.

There is controversy regarding whether total hip arthroplasty (THA) or hemiarthroplasty (HA) is the treatment preferred for displaced intracapsular femoral neck fractures (FNFs). Using the US National Hospital Discharge Survey, we found that, of 12,757 patients admitted for FNF between 2001 and 2010, 4.6% underwent THA and 52.5% underwent HA. More of both procedures were performed over time. Mean age was higher for HA patients. Hospitalization duration and blood transfusion rates were higher for THA. There were region-based differences in frequency of THA and significant hospital-size-based differences in frequency of HA, possibly because of differences in regional training and subspecialist availability. In addition, a larger proportion of THA patients was covered by private insurance.

Flexor Tendon Sheath Engineering Using Decellularized Porcine Pericardium.

BACKGROUND: The flexor tendon sheath is an ideal target for tissue engineering because it is difficult to reconstruct by conventional surgical methods. The authors hypothesized that decellularized porcine pericardium can be used as a scaffold for engineering a biologically active tendon sheath. METHODS: The authors' protocol removed cellular material from the pericardium and preserved the structural architecture in addition to the collagen and glycosaminoglycan content. The scaffold was successfully reseeded with human sheath synoviocytes and human adipose-derived stem cells. Cells were evaluated for 8 weeks after reseeding. RESULTS: The reseeded construct demonstrated continuous production of hyaluronic acid, the main component of synovial fluid. After being seeded on the membrane, adipose-derived stem cells demonstrated down-regulation of collagen I and III and up-regulation of hyaluronan synthase 2. CONCLUSION: The results indicate that decellularized porcine pericardium may be a potential scaffold for engineering a biologically active human tendon sheath.

Total Knee Arthroplasty in Obesity: In-Hospital Outcomes and National Trends.

BACKGROUND: Both the prevalence of obesity and the utilization rate of total knee arthroplasty are increasing. The rate and proportion of total knee arthroplasty (TKA) performed in the setting of obesity/morbid obesity is increasing significantly over time. METHODS: Using International Classification of Diseases-Ninth Revision codes, we searched the National Hospitals Discharge Survey national database for patients admitted for primary TKA between 2001 and 2010. We then used International Classification of Diseases-Ninth Revision codes for obesity (body mass index = 30-40 kg/m2) and morbid obesity (body mass index, ≥ 40 kg/m2) to select the obese cohorts. RESULTS: We found 29,694 nonobese, 2645 obese, and 1150 morbidly obese patients. There was an increase in each group over time. The rate of obesity/morbid obesity was strongly correlated with time. Obese and morbidly obese patients were more likely to be younger, female, diabetic, and have Medicaid than nonobese patients. Obese and morbidly obese patients had shorter hospital stays and higher home discharge rates than nonobese patients. Obese and morbidly obese patients had lower transfusion rates, shorter hospital stays, and no increase in inpatient wound infection or venous thromboembolic complications than nonobese patients. The Midwest region saw a greater burden of obese TKA patients. CONCLUSION: With the right measures and precautions, satisfactory inhospital outcomes are possible in the obese patient after primary TKA. A limitation of this study is short inhospital stay of the index procedure as complications may present later after discharge.

Posterolateral dislocation of the knee: Recognizing an uncommon entity.

Posterolateral dislocations of the knee are rare injuries. Early recognition and emergent open reduction is crucial. A 48-year-old Caucasian male presented with right knee pain and limb swelling 3 d after sustaining a twisting injury in the bathroom. Examination revealed the pathognomonic anteromedial "pucker" sign. Ankle-brachial indices were greater than 1.0 and symmetrical. Radiographs showed a posterolateral dislocation of the right knee. He underwent emergency open reduction without an attempt at closed reduction. Attempts at closed reduction of posterolateral dislocations of the knee are usually impossible because of incarceration of medial soft tissue in the intercondylar notch and may only to delay surgical management and increase the risk of skin necrosis. Magnetic resonance imaging is not crucial in the preoperative period and can lead to delays of up to 24 h. Instead, open reduction should be performed once vascular compromise is excluded.

Methicillin-resistant Staphylococcus aureus infected gluteal compartment syndrome with rhabdomyolysis in a bodybuilder.

Gluteal compartment syndrome (GCS) is a rare condition. We present a case of gluteal muscle strain with hematoma formation, methicillin-resistant Staphylococcus aureus (MRSA) superinfection, leading to acute GCS, rhabdomyolysis and acute kidney injury. This combination of diagnoses has not been reported in the literature. A 36-year-old Caucasian male presented with buttock pain, swelling and fever after lifting weights. Gluteal compartment pressure was markedly elevated compared with the contralateral side. Investigations revealed elevated white blood cell, erythrocyte sedimentation rate, C-reactive protein, creatine kinase, creatinine and lactic acid. Urinalysis was consistent with myoglobinuria. Magnetic resonance imaging showed increased T2 signal in the gluteus maximus and a central hematoma. Cultures taken from the emergency debridement and fasciotomy revealed MRSA. He had repeat, debridement 2 d later, and delayed primary closure 3 d after. GCS is rare and must be suspected when patients present with pain and swelling after an inciting event. They are easily diagnosed with compartment pressure monitoring. The treatment of gluteal abscess and compartment syndrome is the same and involves rapid surgical debridement.

Augmentation of tendon healing with an injectable tendon hydrogel in a rat Achilles tendon model.

BACKGROUND: Many unsolved problems in plastic and hand surgery are related to poor healing of acute and chronic tendon injuries. The authors hypothesized that tendon healing could be augmented by the addition of a tendon-derived, extracellular matrix hydrogel that would guide tissue regeneration. METHODS: Both Achilles tendons of 36 Wistar rats were given full-thickness injuries approximately 5 mm long and 0.5 mm wide from the tendon insertion at the calcaneus to the midsubstance. The hydrogel was injected into the injury site of one leg and compared with control saline in the other. The ultimate failure load, ultimate tensile stress, and stiffness were evaluated at 2, 4, and 8 weeks. Tendon cross-sections underwent histologic analysis (hematoxylin and eosin and picrosirius red) after the animals were killed. Statistical analysis of biomechanical data was performed using a paired t test. RESULTS: There was no significant difference in strength between gel and saline injections in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.42), or stiffness (p = 0.76) at 2 weeks. However, there was a significant difference in ultimate failure load (74.8 ± 11.6 N versus 58.4 ± 14.2 N; p = 0.02) at 4 weeks. The difference in ultimate tensile stress (p = 0.63) and stiffness (p = 0.08) remained insignificant. By 8 weeks, there was no significant difference in strength in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.39), or stiffness (p = 0.75). CONCLUSIONS: Treatment with the tendon hydrogel significantly increases the ultimate failure load of tendons at the critical 4-week time point, and is a promising method for augmentation of tendon healing.

Design and characterization of an injectable tendon hydrogel: a novel scaffold for guided tissue regeneration in the musculoskeletal system.

A biocompatible hydrogel consisting of extracellular matrix (ECM) from human tendons is described as a potential scaffold for guided tissue regeneration and tissue engineering purposes. Lyophilized decellularized tendons were milled and enzymatically digested to form an ECM solution. The ECM solution properties are assessed by proteome analysis with mass spectrometry, and the material's rheological properties are determined as a function of frequency, temperature, and time. In vivo application of the gel in a rat model is assessed for remodeling and host cell repopulation. Histology for macrophage invasion, fibroblast repopulation, and nanoscale properties of the gel is assessed. Gel interaction with multipotent adipoderived stem cells (ASCs) is also addressed in vitro to assess possible cytotoxicity and its ability to act as a delivery vehicle for cells. Proteome analysis of the ECM-solution and gel mass spectroscopy identified the most abundant 150 proteins, of which two isoforms of collagen I represented more than 55% of the sample. Rheology showed that storage (G') and loss (G″) of the ECM solution were stable at room temperature but displayed sigmoidal increases after ∼15 min at 37°C, matching macroscopic observations of its thermo responsiveness. G' and G″ of the gel at 1 rad/s were 213.1±19.9 and 27.1±2.4 Pa, respectively. Electron microscopy revealed fiber alignment and good structural porosity in the gel, as well as invasion of cells in vivo. Histology also showed early CD68(+) macrophage invasion throughout the gel, followed by increasing numbers of fibroblast cells. ASCs mixed with the gel in vitro proliferated, indicating good biocompatibility. This ECM solution can be delivered percutaneously into a zone of tendon injury. After injection, the thermoresponsive behavior of the ECM solution allows it to polymerize and form a porous gel at body temperature. A supportive nanostructure of collagen fibers is established that conforms to the three-dimensional space of the defect. This hydrogel holds the distinctive composition specific for tendon ECM, where tissue-specific cues facilitate host cell infiltration and remodeling. The results presented indicate that injectable ECM materials from tendon may offer a promising alternative in the treatment of tendinopathies and acute tendon injuries.

Reconstruction of the tendon-bone insertion with decellularized tendon-bone composite grafts: comparison with conventional repair.

PURPOSE: Injuries involving the tendon-bone interface (TBI) are difficult to address. Standard techniques typically lead to diminished strength of the healed insertion site. We hypothesized that these injuries would benefit from being reconstructed with decellularized composite grafts replacing both tendon and bone. To test this hypothesis, decellularized grafts were compared with conventional pullout repairs in an in vivo animal model. METHODS: We harvested 48 Achilles TBI grafts from rats and decellularized them. Tendon-bone interface graft reconstruction and pullout repairs were compared using a pair-matched design. Biomechanical properties were evaluated at 2, 4, 8, and 12 weeks. We evaluated histological analysis of insertion morphology and collagen type I/III content. RESULTS: There was a significant increase in ultimate failure load (35 ± 11 vs 24 ± 7 N) and ultimate tensile stress (1.5 ± 0.3 vs 1.0 ± 0.4 N/mm(2)) of the TBI grafts compared with pullout repairs at 2 weeks. These differences remained at 4 weeks. At 12 weeks, both TBI grafts and pullout repairs were as strong as native tissue and not significantly different from each other. Histology showed a more organized extracellular matrix in the TBI graft group at the early time points. Repopulation of the decellularized grafts increased over time. At 12 weeks, the insertion points of both groups were richly populated with cells that possessed morphologies similar to those found in native TBI. CONCLUSIONS: This study showed that decellularized TBI grafts were stronger compared with conventional pullout repairs at 2 and 4 weeks but were comparable at 12 weeks. A more organized extracellular matrix and different collagen composition in the early time points may explain the observed differences in strength. CLINICAL RELEVANCE: In the future, decellularized TBI grafts may be used to reconstruct tendon-bone insertion tears in multiple areas including the flexor tendon system.