Prospective 1-Year Outcomes Are Maintained at Short-Term Final Follow-Up After Superior Capsular Reconstruction Augmentation of Complete Rotator Cuff Repair.

PURPOSE: To evaluate the outcomes of arthroscopic superior capsular reconstruction (SCR) augmentation of complete, massive rotator cuff repair (RCR). METHODS: A retrospective study of dermal allograft SCR-augmented RCRs performed by a single surgeon from June 2016 through December 2017 was performed with the following inclusion criteria: massive rotator cuff tear amenable to complete repair but with poor-quality native rotator cuff tissue. Radiographic follow-up was performed at 1 year, and clinical follow-up was performed at both 1 year and a minimum 2 years after surgery. Clinical follow-up included the American Shoulder and Elbow Surgeons score, visual analog scale score for pain, Subjective Shoulder Value score, active forward elevation, and external rotation. Radiographs and magnetic resonance imaging (MRI) scans were assessed for muscle quality using the Goutallier classification, and graft and cuff integrity was assessed according to the Sugaya classification. RESULTS: The inclusion criteria were met by 24 patients at 1 year and by 18 (75%) at a minimum of 2 years postoperatively. Patient-reported outcomes were improved compared with preoperative data and were maintained at minimum 2-year follow-up, with median American Shoulder and Elbow Surgeons scores of 42.5 (interquartile range [IQR], 30.8-58.7) versus 93.9 (IQR, 82.4-100) (P < .001); median Subjective Shoulder Value scores of 30 (IQR, 20-50) versus 90 (IQR, 86.2-97.2) (P < .001); and median visual analog scale pain scores of 5.5 (IQR, 1-9) versus 0 (IQR, 0-0.8) (P = .001). Evaluation of graft and tendon healing on postoperative MRI revealed poor interobserver agreement and showed 10 completely healed grafts (42%), 9 partially healed grafts (38%), and 5 completely disrupted grafts (21%), with 42% of supraspinatus tendons and 54% of infraspinatus tendons healed. CONCLUSIONS: SCR with dermal allograft augmentation of complete RCR with poor-quality tissue shows very good clinical outcomes at minimum 2-year follow-up. Poor interobserver agreement regarding postoperative graft and rotator cuff integrity by MRI was found. The healing rate for the SCR grafts was 79%. The rates of healing of the native supraspinatus and infraspinatus tendons were 42% and 54%, respectively. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Micro-CT dilatometry measures of molecular collagen hydration using bovine extensor tendon.

PURPOSE: This article introduces a new method to study macromolecular hydration using micro-CT dilatometry. The complexity of hydration dependence on solvent temperature, pH, ionic charge, ionic activity, and ionic radii are barriers to comprehensive understanding of protein function. The crystalline character of collagen-tendon suggests that tendon dilatometry may give direct access to measures of molecular tropocollagen solvation response. METHODS: The molecular basis of the stoichiometric hydration model (SHM) provides tools to validate bovine tendon as a model to study protein-solvent shape response by micro-CT measures of tendon diameter, length, and mass during dehydration. The SHM relates macroscopic properties to molecular properties of water interacting with the surface of collagen molecules. There are marked changes at critical SHM hydration levels h = 0.0653, 0.262, and 0.724 g water/g dry weight. RESULTS: Micro-CT analysis of the length, diameter, and volume combined with gravimetric measures of tendon mass as a function of hydration h (g water/g dry solid) shows asymmetric changes in length, diameter, and density as predicted by SHM. The collagen molecules perturb water properties of polar hydration N=11 waters per tripeptide unit or h approximately 0.724 g/g to confirm MDS prediction of elevated hydration density 20%-50% higher than bulk water. CONCLUSIONS: Results validate the use of tendon dilatometry amplification factors of 10(6)-10(8) as an effective model to investigate protein molecule shape change response to solvent molecules. The tendon model for the first time allows direct study of protein hydration and functional response under physiological conditions.

Imaging of the diabetic foot diagnostic dilemmas.

Multiple diagnostic imaging modalities are available and beneficial for the evaluation of the diabetic foot. There is not yet "one best test" for sorting out the diagnostic dilemmas commonly encountered. The differentiation of cellulitis alone from underlying osteomyelitis and the early detection of abscesses remain important diagnostic goals. Equally important, differentiation of osteomyelitis and neuroarthropathy remains a difficult job. This is often compounded by postoperative diabetic foot states status after reconstruction. Diagnostic evaluation often involves multiple studies that are complementary and that include conventional radiography, computed tomography, nuclear medicine scintigraphy, magnetic resonance imaging, ultrasonography, and positron emission tomography.

Collagen structure: the molecular source of the tendon magic angle effect.

This review of tendon/collagen structure shows that the orientational variation in MRI signals from tendon, which is referred to as the "magic angle" (MA) effect, is caused by irreducible separation of charges on the main chain of the collagen molecule. These charges are held apart in a vacuum by stereotactic restriction of protein folding due in large part to a high concentration of hydroxyproline ring residues in the amino acids of mammalian collagen. The elevated protein electrostatic energy is reduced in water by the large dielectric constant of the highly polar solvent (kappa approximately 80). The water molecules serve as dielectric molecules that are bound by an energy that is nearly equivalent to the electrostatic energy between the neighboring positive and negative charge pairs in a vacuum. These highly immobilized water molecules and secondary molecules in the hydrogen-bonded water network are confined to the transverse plane of the tendon. Orientational restriction causes residual dipole coupling, which is directly responsible for the frequency and phase shifts observed in orientational MRI (OMRI) described by the MA effect. Reference to a wide range of biophysical measurements shows that native hydration is a monolayer on collagen h(m) = 1.6 g/g, which divides into two components consisting of primary hydration on polar surfaces h(pp) = 0.8 g/g and secondary hydration h(s) = 0.8 g/g bridging over hydrophobic surface regions. Primary hydration further divides into side-chain hydration h(psc) = 0.54 g/g and main-chain hydration h(pmc) = 0.263 g/g. The main-chain fraction consists of water that bridges between charges on the main chain and is responsible for almost all of the enthalpy of melting DeltaH = 70 J/g-dry mass. Main-chain water bridges consist of one extremely immobilized Ramachandran water bridge per tripeptide h(Ra) = 0.0658 g/g and one double water bridge per tripeptide h(dwb) = 0.1974 g/g, with three water molecules that are sufficiently slowed to act as the spin-lattice relaxation sink for the entire tendon.

The magic angle effect: a source of artifact, determinant of image contrast, and technique for imaging.

This review provides a formalism for understanding magic angle effects in clinical studies. It involves consideration of the fiber-to-field angle for linear structures such as tendons, ligaments, and peripheral nerves, disc-like and circular structures such as menisci and labra, as well as complex three-dimensional structures. There may be one or more fiber types with different orientations within each of these tissues. The orientation of these fibers to B(0) is crucial in determining their magic angle effect. Tissues may show a variety of appearances depending on their baseline T2, as well as the increase in T2 produced by the magic angle effect. The appearances are affected by TE, which affects both the general tissue signal level and the change in signal produced by the magic angle effect, fiber-to-slice orientation, and partial volume effects. Deliberate positioning of structures and tissues at particular orientations to B(0) can be used to increase the signal from tissues such as tendons and ligaments and so allow them to be imaged with conventional sequences. The technique can also be used to produce contrast between tissues with fibers that have different orientations to B(0).

An NMR method to characterize multiple water compartments on mammalian collagen.

A molecular model is proposed to explain water 1H NMR spin-lattice relaxation at different levels of hydration (NMR titration method) on collagen. A fast proton exchange model is used to identify and characterize protein hydration compartments at three distinct Gibbs free energy levels. The NMR titration method reveals a spectrum of water motions with three well-separated peaks in addition to bulk water that can be uniquely characterized by sequential dehydration. Categorical changes in water motion occur at critical hydration levels h (g water/g collagen) defined by integral multiples N = 1, 4 and 24 times the fundamental hydration value of one water bridge per every three amino acid residues as originally proposed by Ramachandran in 1968. Changes occur at (1) the Ramachandran single water bridge between a positive amide and negative carbonyl group at h1 = 0.0658 g/g, (2) the Berendsen single water chain per cleft at h2 = 0.264 g/g, and (3) full monolayer coverage with six water chains per cleft level at h3 = 1.584 g/g. The NMR titration method is verified by comparison of measured NMR relaxation compartments with molecular hydration compartments predicted from models of collagen structure. NMR titration studies of globular proteins using the hydration model may provide unique insight into the critical contributions of hydration to protein folding.

Radiofrequency ablation of hepatic tumors: variability of lesion size using a single ablation device.

OBJECTIVE: In this study, we examined the variability of lesion sizes produced by a single radiofrequency ablation using the same device and algorithm in patients with small malignant hepatic tumors. MATERIALS AND METHODS: A review of the clinical records of 208 patients who underwent radiofrequency ablation of malignant hepatic tumors during a 6-year period revealed 31 patients with small tumors that were treated with a single ablation. Clinical data were recorded using standardized work sheets. Tumor and lesion sizes after ablation were measured from CT scans. The influences of tumor size, tumor type, presence or absence of cirrhosis, and tissue temperature on the ablation size were analyzed. RESULTS: The size of tumor before treatment ranged from 0.8 to 4.0 cm (mean diameter [+/- SD] = 1.8 +/- 0.9 cm) with corresponding volumes of 0.27-30.24 mL (mean volume = 27.1 +/- 15.9 mL). The lesion sizes after ablation ranged from 1.7 to 5.3 cm (mean diameter = 3.6 +/- 0.7 cm) with corresponding volumes of 2.29-75.87 mL (mean volume = 4.9 +/- 7.1 mL). Tumor type (p > 0.25), presence or absence of cirrhosis (p > 0.45), and tissue temperature (p = 0.055) had no relationship to ablation size. Tumor size had a statistically significant influence on ablation lesion size (p < 0.04). Ablation of small tumors (diameter < or = 2.25 cm, n = 32) produced random lesion sizes whereas ablation of large tumors (diameter > 2.25 cm, n = 11) produced larger lesions (mean diameter = 4.0 +/- 0.8 cm). CONCLUSION: Significant variation occurs in the lesion size produced using the same ablation device and algorithm. These findings must be considered when planning ablation strategies.