SummaryA widely shared view reads that mesenchymal stem/stromal cells (“MSCs”) are ubiquitous in human connective tissues, can be defined by a common in vitro phenotype, share a skeletogenic potential as assessed by in vitro differentiation assays, and coincide with ubiquitous pericytes. Using stringent in vivo differentiation assays and transcriptome analysis, we show that human cell populations from different anatomical sources, regarded as “MSCs” based on these criteria and assumptions, actually differ widely in their transcriptomic signature and in vivo differentiation potential. In contrast, they share the capacity to guide the assembly of functional microvessels in vivo, regardless of their anatomical source, or in situ identity as perivascular or circulating cells. This analysis reveals that muscle pericytes, which are not spontaneously osteochondrogenic as previously claimed, may indeed coincide with an ectopic perivascular subset of committed myogenic cells similar to satellite cells. Cord blood-derived stromal cells, on the other hand, display the unique capacity to form cartilage in vivo spontaneously, in addition to an assayable osteogenic capacity. These data suggest the need to revise current misconceptions on the origin and function of so-called “MSCs,” with important applicative implications. The data also support the view that rather than a uniform class of “MSCs,” different mesoderm derivatives include distinct classes of tissue-specific committed progenitors, possibly of different developmental origin.

The use of the platelet-leukocyte membrane in the treatment of rotator cuff tears improved repair integrity compared with repair without membrane. However, the improvement in repair integrity was not associated with greater improvement in the functional outcome. In fact, the Constant scores of the two groups would have been similar if the shoulder pain component (which had differed preoperatively) had been excluded.

We have studied, prospectively, 116 patients with motor deficits associated with herniation of a lumbar disc who underwent microdiscectomy. They were studied during the first six months and at a mean of 6.4 years after surgery. Before operation, muscle weakness was mild (grade 4) in 67% of patients, severe (grade 3) in 21% and very severe (grade 2 or 1) in 12%. The muscle which most frequently had severe or very severe weakness was extensor hallucis longus, followed in order by triceps surae, extensor digitorum communis, tibialis anterior, and others. At the latest follow-up examination, 76% of patients had complete recovery of strength. Persistent weakness was found in 16% of patients who had had a mild preoperative deficit and in 39% of those with severe or very severe weakness. Muscle strength was graded 4 in all patients with persistent weakness, except for four with a very severe preoperative deficit affecting the L5 or S1 nerve root. They showed no significant recovery. Excluding this last group, the degree of recovery of motor function was inversely related to the preoperative severity and duration of muscle weakness. The patients' subjective functional capacity was not directly related to the degree of recovery except in those with persistent severe or very severe deficit.

We have studied, prospectively, 116 patients with motor deficits associated with herniation of a lumbar disc who underwent microdiscectomy. They were studied during the first six months and at a mean of 6.4 years after surgery. Before operation, muscle weakness was mild (grade 4) in 67% of patients, severe (grade 3) in 21% and very severe (grade 2 or 1) in 12%. The muscle which most frequently had severe or very severe weakness was extensor hallucis longus, followed in order by triceps surae, extensor digitorum communis, tibialis anterior, and others. At the latest follow-up examination, 76% of patients had complete recovery of strength. Persistent weakness was found in 16% of patients who had had a mild preoperative deficit and in 39% of those with severe or very severe weakness. Muscle strength was graded 4 in all patients with persistent weakness, except for four with a very severe preoperative deficit affecting the L5 or S1 nerve root. They showed no significant recovery. Excluding this last group, the degree of recovery of motor function was inversely related to the preoperative severity and duration of muscle weakness. The patients’ subjective functional capacity was not directly related to the degree of recovery except in those with persistent severe or very severe deficit.

Complex elbow instability is a challenging injury even for expert elbow surgeons. The preoperative radiographs should be carefully evaluated to recognize all lesions that may occur in complex elbow instabilities. Recognizing all the possible lesions is critical to achieve an optimal outcome. The most common types of injuries are as follows: (1) radial head fractures associated with lateral and medial collateral ligaments lesions (with or without elbow dislocation); (2) Coronoid fractures and lateral collateral ligament lesion (with or without elbow dislocation); (3) Terrible Triad; (4) Transolecranon fracture-dislocation; (5) Monteggia-like-lesions; and (6) Humeral Shear fractures associated with lateral and medial collateral ligaments lesions (with or without elbow dislocation). A correct evaluation includes X-rays, CT scan with 2D and 3D reconstruction and stability test under fluoroscopy. The treatment is always surgical and is challenging, and outcomes are not predictable. The goals of treatment are (1) to perform a stable osteosynthesis of all fractures, (2) to obtain concentric and stable reduction of the elbow and (3) to allow early motion. The proximal ulna must be anatomically reduced and fixed; the radial head must be repaired or replaced, and the coronoid fractures must be repaired or reconstructed. With respect of soft tissue lesions, the LUCL must be reattached with suture anchors or trans-osseous suture. The next critical step is the intra-operative assessment of elbow stability. If the elbow remains unstable, MCL repair and/or application of hinged external fixator must be considered. The most recent clinical and experimental studies have significantly expanded our knowledge of elbow instability and its management. Definite treatment protocols may improve the clinical results of such complex injuries.

Level IV. Historical series.

The aim of this study was to address, in normal knees, the variability of posterior offset of femoral condyles and tibial slope, and the presence of any correlation between the two that might be needed to achieve an adequate joint motion in flexion. Magnetic resonance images of normal knees of 80 subjects, 45 males and 35 females, with a mean age of 38.9 years, were analysed. Measurements were performed by two independent observers using an imaging visualization software. The tibial slope averaged 8 and 7.7°, on the medial and lateral sides, respectively (P = 0.2); the mean posterior offset of femoral condyles was 27.4 and 25.2 mm on the two sides, respectively (P = 0.0001). The variation coefficient of the condylar offset and tibial slope was 11.5 and 38%, respectively. In the medial compartment, a significant correlation was found between the femoral condylar offset and the tibial slope, while the same was not observed in the lateral compartment of the knee. Magnetic resonance imaging allows the assessment of tibial slope and femoral condylar offset in the medial and lateral side separately, taking into account any difference between the two compartments. The sagittal tibial slope exhibits a greater variability compared with the posterior offset of femoral condyles. The correlation found, in the medial compartment, between the tibial slope and femoral condylar offset suggests that the reconstitution of the proper morphology of the posterior part of the knee joint may be necessary to obtain a full range of motion in flexion after total knee replacement.

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