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Janine Molino,1,2 Joseph Harrington,2 Jennifer Racine-Avila,2 Roy Aaron2 1Lifespan Biostatistics Core, Rhode Island Hospital, Providence, RI, USA; 2Department of Orthopedic Surgery, Warren Alpert Medical School of Brown University, Providence, RI, USACorrespondence: Roy Aaron, Email Roy_Aaron@Brown.eduPurpose: The minimal clinically important difference (MCID) is a way of dichotomizing data for assessment of success or failure based on clinically meaningful changes. The magnitude of the MCID is often misunderstood to be a singular quantity applicable across studies. However, substantial differences have been reported among MCIDs for the same outcome measures usually based upon differences extrinsic to the calculation. This study explores the effects of variabilities intrinsic to the calculation of the MCID.Methods: The MCIDs for two knee replacement patient-reported outcomes measures of pain and function were calculated at 1 year postoperative with an integrative anchor and distribution-based method using external anchor questions and receiver operator characteristic (ROC) curves. The effects upon the magnitude and precision of the MCIDs of varying the anchor questions, the thresholds for success/failure, and the sample sizes were examined.Results: Wide variabilities were observed in both the magnitudes and precision of the MCIDs. The threshold for success had the largest effect on magnitude of pain scores, while the sample size had the largest effect on precision. For function scores, the sample size had the largest effect on magnitude, and the anchor question had the largest effect on precision.Conclusion: Comparisons among MCIDs are difficult to interpret if elements of the calculations are different and influence the results. While factors extrinsic to the calculations, e.g., study population, trial design, methods of calculation, etc., are known to produce differences in the magnitude of MCIDs, this study shows that more subtle and less obvious factors intrinsic to the calculations have profound effects on both the magnitude and precision of MCIDs. Comparisons among MCIDs should be made with caution and call for greater transparency in reporting intrinsic methods. It is probably advisable for individual studies to calculate their own MCIDs and not rely on published values.Keywords: outcome assessment, categorical measure, clinical improvement

Understanding global body balance can optimize the postoperative course for patients undergoing spinal or lower limb surgical realignment. This observational cohort study aimed to characterize patients with reported imbalance and identify predictors. The CDC establishes a representative sample annually via the NHANES. All participants who said “yes” (Imbalanced) or “no” (Balanced) to the following question were identified from 1999–2004: “During the past 12 months, have you had dizziness, difficulty with balance or difficulty with falling?” Univariate analyses compared Imbalanced versus Balanced subjects and binary logistic regression modeling predicted for Imbalance. Of 9964 patients, imbalanced (26.5%) were older (65.4 vs. 60.6 years), with more females (60% vs. 48%). Imbalanced subjects reported higher rates of comorbidities, including osteoporosis (14.4% vs. 6.6%), arthritis (51.6% vs. 31.9%), and low back pain (54.4% vs 32.7%). Imbalanced patients had more difficulty with activities, including climbing 10 steps (43.8% vs. 21%) and stooping/crouching/kneeling (74.3% vs. 44.7%), and they needed greater time to walk 20 feet (9.5 vs. 7.1 s). Imbalanced subjects had significantly lower caloric and dietary intake. Regression revealed that difficulties using fingers to grasp small objects (OR: 1.73), female gender (OR: 1.43), difficulties with prolonged standing (OR: 1.29), difficulties stooping/crouching/kneeling (OR: 1.28), and increased time to walk 20 feet (OR: 1.06) were independent predictors of Imbalance (all p < 0.05). Imbalanced patients were found to have identifiable comorbidities and were detectable using simple functional assessments. Structured tests that assess dynamic functional status may be useful for preoperative optimization and risk-stratification for patients undergoing spinal or lower limb surgical realignment.

The roles of a fracture liaison service (FLS) are extensive and include, but are not limited to: 1) providing a standardized framework for the evaluation and management of low-energy fractures, also known as fragility fractures; 2) improving patient outcomes through the recognition of fragility fractures as signal events requiring further diagnostic explanation; and 3) lowering direct and indirect healthcare expenditures. One of the central tenets of the FLS is its recognition of fragility fractures as warning signs of underlying pathology, often osteoporosis or other metabolic bone diseases. This understanding, combined with the application of a multidisciplinary management team specialized in diagnosing and treating such pathologies, allows for better short- and long-term management of patients and concordant improvement in outcomes. This article should be viewed as a thematic introduction to the FLS, with others in this volume each illustrating specific examples of how FLS paradigms facilitate the roles described herein.

Osteomalacia is defined by the undermineralization of newly formed bone due to a lack of available calcium, phosphorus, or vitamin D. Causative factors of osteomalacia include nutritional deficiency, diminished absorptive capabilities (often due to gastrointestinal disorders), and renal insufficiency. Renal osteodystrophy is a specific form of metabolic bone disease defined by the presence of osteomalacia and associated hyperparathyroidism secondary to a malfunction in, or absence of, renal parenchyma. This reduces the conversion of vitamin D to its active form, thus leading to a cascade of effects that negatively impact the stability of the skeleton. Osteomalacia occurs across a spectrum of severity and can produce severe consequences for specific populations, including patients with dietary, nutritional, and absorptive deficiencies. Renal osteodystrophy affects patients with chronic kidney disease, those undergoing dialysis, and renal transplant patients. Special considerations must be taken into account when assessing the bone health of patients fitting these criteria.

Bone marrow edema (BME), also termed bone marrow lesions, is a syndrome characterized by bone pain and the appearance of high signal intensity on T2 fat-suppressed and short tau inversion recovery (STIR) MRI sequences. BME can be related to trauma or a variety of non-traumatic diseases, and current treatment modalities include non-steroidal anti-inflammatory drugs (NSAIDS), bisphosphonates, denosumab, extracorporeal shockwave therapy (ESWT), the vasoactive prostacyclin analogue iloprost, and surgical decompression. Spontaneous BME is a subset that has been observed with no apparent causative conditions. It is most likely caused by venous outflow obstruction and intraosseous hypertension. These are mechanistically related to impaired perfusion and ischemia in several models of BME and are related to bone remodeling. The association of perfusion abnormalities and bone pain provides the pathophysiological rationale for surgical decompression. We present a case of spontaneous BME and a second case of spontaneous migratory BME treated with surgical decompression and demonstrate resolution of pain and the high signal intensity on MRI. This report provides an integration of the clinical syndrome, MR imaging characteristics, circulatory pathophysiology, and treatment. It draws upon several studies to suggest that both the bone pain and the MRI characteristics are related to venous stasis, and when circulatory pathologies are relieved by decompression or fenestration, both the bone pain and the MRI signal abnormalities resolve.

Notable characteristics of the skeleton are its responsiveness to physical stimuli and its ability to remodel secondary to changing biophysical environments and thereby fulfill its physiological roles of stability and movement. Bone and cartilage cells have many mechanisms to sense physical cues and activate a variety of genes to synthesize structural molecules to remodel their extracellular matrix and soluble molecules for paracrine signaling. This review describes the response of a developmental model of endochondral bone formation which is translationally relevant to embryogenesis, growth, and repair to an externally applied pulsed electromagnetic field (PEMF). The use of a PEMF allows for the exploration of morphogenesis in the absence of distracting stimuli such as mechanical load and fluid flow. The response of the system is described in terms of the cell differentiation and extracellular matrix synthesis in chondrogenesis. Emphasis is placed upon dosimetry of the applied physical stimulus and some of the mechanisms of tissue response through a developmental process of maturation. PEMFs are used clinically for bone repair and have other potential clinical applications. These features of tissue response and signal dosimetry can be extrapolated to the design of clinically optimal stimulation.

Considerable interest has been expressed in the use of bisphosphonates to treat periprosthetic osteoporosis with the clinical goals of reducing periprosthetic fractures and prolonging implant survival.A systematic review was performed with the goal of identifying both basic science and clinical studies related to the risks and benefits of bisphosphonate use in total joint arthroplasty.Studies have shown that bisphosphonates may increase early bony ingrowth, decrease the postoperative loss of bone mineral density, and increase the longevity of implants by reducing the need for revisions secondary to aseptic loosening. Continuing bisphosphonates for 1 year postoperatively seems to provide the greatest benefit, with only marginal benefit being shown by continuing therapy for up to 2 years. Current data present some concerns for an increased risk of periprosthetic fractures especially in younger patients, and prolonged therapy is not recommended due to the potential risk of atypical femur fractures. Patients should be counseled regarding the risk of side effects of bisphosphonates, including the risk of osteonecrosis of the jaw, which is a rare but serious side effect. They should also be counseled on the risk of atypical femur fractures and gastrointestinal intolerance.Orthopedic surgeons could consider bisphosphonates for up to 1 year postoperatively regardless of the patient's prior bone mineral density, after discussion regarding the risks and benefits with the patient.

A prominent feature of the skeleton is its ability to remodel in response to biophysical stimuli and to repair under varied biophysical conditions. This allows the skeleton considerable adaptation to meet its physiological roles of stability and movement. Skeletal cells and their mesenchymal precursors exist in a native environment rich with biophysical signals, and they sense and respond to those signals to meet organismal demands of the skeleton. While mechanical strain is the most recognized of the skeletal biophysical stimuli, signaling phenomena also include fluid flow, hydrostatic pressure, shear stress, and ion-movement-related electrokinetic phenomena including, prominently, streaming potentials. Because of the complex interactions of these electromechanical signals, it is difficult to isolate the significance of each. The application of external electrical and electromagnetic fields allows an exploration of the effects of these stimuli on cell differentiation and extra-cellular matrix formation in the absence of mechanical strain. This review takes a distinctly translational approach to mechanistic and preclinical studies of differentiation and skeletal lineage commitment of mesenchymal cells under biophysical stimulation. In vitro studies facilitate the examination of isolated cellular responses while in vivo studies permit the observation of cell differentiation and extracellular matrix synthesis.