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Open Access Publications from the University of California

Open Access Policy Deposits

This series is automatically populated with publications deposited by UCSF Department of Orthopaedic Surgery researchers in accordance with the University of California’s open access policies. For more information see Open Access Policy Deposits and the UC Publication Management System.

Cover page of Adolescent Tibial Tubercle Fracture: Review of Outcomes and Complications.

Adolescent Tibial Tubercle Fracture: Review of Outcomes and Complications.


PURPOSE OF REVIEW: Fractures of the tibial tubercle are a relatively uncommon injury, representing 3% of all proximal tibia fractures and < 1% of all physeal fractures, primarily seen in the adolescent demographic. While recognition of the injury and its management is being more widely reported in the literature and recognized in the hospital setting, reports of its outcomes and complications have still been limited. This article provides an updated review of the outcomes and complications of tibial tubercle fractures. RECENT FINDINGS: Current research shows both radiographic outcomes, specifically osseous union, and functional outcomes, such as return to play and full knee range of motion, are excellent in patients treated either operatively or nonoperatively. Complication rates overall remain relatively low, with the most common complication being bursitis and hardware prominence and the most common associated injuries being patellar tendon avulsions and meniscus tears. With appropriate management, tibial tubercle fractures have an excellent overall outcome and a low complication rate. Although complications are uncommon, treating providers should be vigilant and recognize the signs of devastating complications resulting from acute vascular injuries or compartment syndrome. Further research should aim to analyze patients experiences and satisfaction following treatment of this injury and examine the long-term functional and patient-reported outcomes.

Cover page of 3D Printing Technology in Pediatric Orthopedics: a Primer for the Clinician.

3D Printing Technology in Pediatric Orthopedics: a Primer for the Clinician.


PURPOSE OF REVIEW: This article reviews the basics of 3D printing and provides an overview of current and future applications of this emerging technology in pediatric orthopedic surgery. RECENT FINDINGS: Both preoperative and intraoperative utilization of 3D printing technology have enhanced clinical care. Potential benefits include more accurate surgical planning, shortening of a surgical learning curve, decrease in intraoperative blood loss, less operative time, and fluoroscopic time. Furthermore, patient-specific instrumentation can be used to improve the safety and accuracy of surgical care. Patient-physician communication can also benefit from 3D printing technology. 3D printing is rapidly advancing in the field of pediatric orthopedic surgery. It has the potential to increase the value of several pediatric orthopedic procedures by enhancing safety and accuracy while saving time. Future efforts in cost reduction strategies, making patient-specific implants including biologic substitutes and scaffolds, will further increase the relevance of 3D technology in the field of pediatric orthopedic surgery.

Cover page of Theoretical Schemas to Guide Back Pain Consortium (BACPAC) Chronic Low Back Pain Clinical Research.

Theoretical Schemas to Guide Back Pain Consortium (BACPAC) Chronic Low Back Pain Clinical Research.


BACKGROUND: Chronic low back pain (cLBP) is a complex with a heterogenous clinical presentation. A better understanding of the factors that contribute to cLBP is needed for accurate diagnosis, optimal treatment, and identification of mechanistic targets for new therapies. The Back Pain Consortium (BACPAC) Research Program provides a unique opportunity in this regard, as it will generate large clinical datasets, including a diverse set of harmonized measurements. The Theoretical Model Working Group was established to guide BACPAC research and to organize new knowledge within a mechanistic framework. This article summarizes the initial work of the Theoretical Model Working Group. It includes a three-stage integration of expert opinion and an umbrella literature review of factors that affect cLBP severity and chronicity. METHODS: During Stage 1, experts from across BACPAC established a taxonomy for risk and prognostic factors (RPFs) and preliminary graphical depictions. During Stage 2, a separate team conducted a literature review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to establish working definitions, associated data elements, and overall strength of evidence for identified RPFs. These were subsequently integrated with expert opinion during Stage 3. RESULTS: The majority (∼80%) of RPFs had little strength-of-evidence confidence, whereas seven factors had substantial confidence for either a positive association with cLBP (pain-related anxiety, serum C-reactive protein, diabetes, and anticipatory/compensatory postural adjustments) or no association with cLBP (serum interleukin 1-beta / interleukin 6, transversus muscle morphology/activity, and quantitative sensory testing). CONCLUSION: This theoretical perspective will evolve over time as BACPAC investigators link empirical results to theory, challenge current ideas of the biopsychosocial model, and use a systems approach to develop tools and algorithms that disentangle the dynamic interactions among cLBP factors.

Cover page of Biomechanical Phenotyping of Chronic Low Back Pain: Protocol for BACPAC.

Biomechanical Phenotyping of Chronic Low Back Pain: Protocol for BACPAC.


OBJECTIVE: Biomechanics represents the common final output through which all biopsychosocial constructs of back pain must pass, making it a rich target for phenotyping. To exploit this feature, several sites within the NIH Back Pain Consortium (BACPAC) have developed biomechanics measurement and phenotyping tools. The overall aims of this article were to: 1) provide a narrative review of biomechanics as a phenotyping tool; 2) describe the diverse array of tools and outcome measures that exist within BACPAC; and 3) highlight how leveraging these technologies with the other data collected within BACPAC could elucidate the relationship between biomechanics and other metrics used to characterize low back pain (LBP). METHODS: The narrative review highlights how biomechanical outcomes can discriminate between those with and without LBP, as well as among levels of severity of LBP. It also addresses how biomechanical outcomes track with functional improvements in LBP. Additionally, we present the clinical use case for biomechanical outcome measures that can be met via emerging technologies. RESULTS: To answer the need for measuring biomechanical performance, our Results section describes the spectrum of technologies that have been developed and are being used within BACPAC. CONCLUSION AND FUTURE DIRECTIONS: The outcome measures collected by these technologies will be an integral part of longitudinal and cross-sectional studies conducted in BACPAC. Linking these measures with other biopsychosocial data collected within BACPAC increases our potential to use biomechanics as a tool for understanding the mechanisms of LBP, phenotyping unique LBP subgroups, and matching these individuals with an appropriate treatment paradigm.

Cover page of The Back Pain Consortium (BACPAC) Research Program: Structure, Research Priorities, and Methods.

The Back Pain Consortium (BACPAC) Research Program: Structure, Research Priorities, and Methods.


In 2019, the National Health Interview survey found that nearly 59% of adults reported pain some, most, or every day in the past 3 months, with 39% reporting back pain, making back pain the most prevalent source of pain, and a significant issue among adults. Often, identifying a direct, treatable cause for back pain is challenging, especially as it is often attributed to complex, multifaceted issues involving biological, psychological, and social components. Due to the difficulty in treating the true cause of chronic low back pain (cLBP), an over-reliance on opioid pain medications among cLBP patients has developed, which is associated with increased prevalence of opioid use disorder and increased risk of death. To combat the rise of opioid-related deaths, the National Institutes of Health (NIH) initiated the Helping to End Addiction Long-TermSM (HEAL) initiative, whose goal is to address the causes and treatment of opioid use disorder while also seeking to better understand, diagnose, and treat chronic pain. The NIH Back Pain Consortium (BACPAC) Research Program, a network of 14 funded entities, was launched as a part of the HEAL initiative to help address limitations surrounding the diagnosis and treatment of cLBP. This paper provides an overview of the BACPAC research programs goals and overall structure, and describes the harmonization efforts across the consortium, define its research agenda, and develop a collaborative project which utilizes the strengths of the network. The purpose of this paper is to serve as a blueprint for other consortia tasked with the advancement of pain related science.

Cover page of Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group.

Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group.


Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Research Program Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing magnetic resonance imaging (MRI) acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.

Cover page of A Case of Hypercalcemia from PTHrP-Producing Fibromyxoid Sarcoma Responsive to Glucocorticoid Therapy.

A Case of Hypercalcemia from PTHrP-Producing Fibromyxoid Sarcoma Responsive to Glucocorticoid Therapy.


The treatment of parathyroid hormone-related protein (PTHrP)-mediated hypercalcemia of malignancy includes treating the malignancy, intravenous fluids, and anti-resorptive therapies such as zoledronic acid or denosumab. PTHrP-mediated hypercalcemia has been reported in benign conditions such as systemic lupus erythematous (SLE) and sarcoidosis and appears to be responsive to glucocorticoids. We report a case of PTHrP-induced hypercalcemia due to a malignancy-low grade fibromyxoid sarcoma-that responded to glucocorticoid treatment. This is the first report of glucocorticoids controlling PTHrP-mediated hypercalcemia of malignancy. Immunohistochemistry of the surgical pathology localized PTHrP staining to the vascular endothelial cells within the tumor. Further studies are needed to elucidate the mechanism of glucocorticoid action in the treatment of PTHrP-mediated hypercalcemia of malignancy.

Cover page of Preventing and Treating Infection in Reverse Total Shoulder Arthroplasty.

Preventing and Treating Infection in Reverse Total Shoulder Arthroplasty.


PURPOSE OF REVIEW: Periprosthetic infection after shoulder arthroplasty is relatively uncommon though associated with severe long-term morbidity when encountered. The purpose of the review is to summarize the recent literature regarding the definition, clinical evaluation, prevention, and management of prosthetic joint infection after reverse shoulder arthroplasty. RECENT FINDINGS: The landmark report generated at the 2018 International Consensus Meeting on Musculoskeletal Infection has provided a framework for diagnosis, prevention, and management of periprosthetic infections after shoulder arthroplasty. Shoulder specific literature with validated interventions to reduce prosthetic joint infection is limited; however existing literature from retrospective studies and from total hip and knee arthroplasty allows us to make relative guidelines. One and two-stage revisions seem to demonstrate similar outcomes; however, no controlled comparative studies exist limiting the ability to make definitive recommendations between the two options. We report on recent literature regarding the current diagnostic, preventative, and treatment options for periprosthetic infection after shoulder arthroplasty. Much of the literature does not distinguish between anatomic and reverse shoulder arthroplasty, and further high-level shoulder specific studies are needed to answer questions generated from this review.

Cover page of Non-specific recognition of histone modifications by H3K9bhb antibody.

Non-specific recognition of histone modifications by H3K9bhb antibody.


Ketone bodies are short-chain fatty acids produced in the liver during periods of limited glucose availability that provide an alternative energy source for the brain, heart, and skeletal muscle. Beyond this metabolic role, β-hydroxybutyrate (BHB), is gaining recognition as a signaling molecule. Lysine β-hydroxybutyrylation (Kbhb) is a newly discovered post-translational modification in which BHB is covalently attached to lysine ε-amino groups. This protein adduct is metabolically sensitive, dependent on BHB concentration, and found on proteins in multiple intracellular compartments. Therefore, Kbhb is hypothesized to be an important component of ketone body-regulated physiology. Kbhb on histones is proposed to be an epigenetic regulator, which links metabolic alterations to gene expression. However, we found that the widely used antibody against β-hydroxybutyrylated lysine 9 on histone H3 (H3K9bhb) also recognizes other modification(s) that likely include acetylation. Therefore, caution must be used when interpreting gene regulation data acquired with the H3K9bhb antibody.

Spine Surgeons Social Dilemma: Benefits and Risks of Social Media for Spine Surgery Practice in the 21st Century.


STUDY DESIGN: Cross-sectional observational. BACKGROUND: The use of social media by providers can enhance patient education, complement offline information, facilitate patient support, stimulate brand building, and strengthen the organizations market position. Risks of social media include, but are not limited to, a lack of quality, reliability, misrepresentation of credentials, influence of hidden and overt conflicts of interest, content that may jeopardize patient privacy, HIPAA regulations, and physicians credentials and licensure. Physicians use of social media may also expose him/her to lawsuits if providing specific medical advice on media platforms. OBJECTIVE: To document the social media presence of a broad cohort of spine surgeons, and to discuss the benefits and risks of a social media presence. METHODS: Cross-sectional observational of 325 Spine Surgeons from 76 institutions across the US. Description statistic and Pearsons correlation were used to investigate the relationships between the variables. RESULTS: Out of the 325 surgeons, 96% were male with an average age of 51.5 ± 10.7 years and 14.1 ± 9.6 years of experience. The frequency of social media use included 57.2% of surgeons had professional LinkedIn, 17.8% had professional Facebook, and less than 16% had other social media platforms. When combining all platforms together, 64.6% of all surgeons had at least one professional social media platform. 64.0% of these surgeons had no social media activity in the past 90 days, while 19.4% and 10.9% were active once and twice a month, respectively. Surgeon age (P = 0.004), years in practice (P < 0.001), and practice type (P < 0.001) were strongly correlated with social media activity. CONCLUSIONS: Given the scarcity of research on this topic and the novelty of the platforms, social media and online services continue to be utilized at a low level by spine surgeons. Issues regarding the risks of privacy issues with social media users continue to be a concern among medical professionals adopting this technology. This can largely be mitigated with the combination of physician education and informed consent from patients. The ability to connect with patients directly, and provide access to high-quality education and information will be of considerable benefit to our field well into the future.