PubMed · 5510969
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S Tasaka, S Takeda, K Teraoka, T Takahashi, M Nishizawa. 1970. [Symposium: tomography].. https://pubmed.ncbi.nlm.nih.gov/5510969/
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Digits of the hand vary from each other with respect to bone and joint architecture, muscles, tendons, and degree of functional independence. The hand may be conceived as having a central rigid framework moved at the wrist by flexors, extensors, abductors, and adductors. But on each side of this central structure lies a mobile (hinged) segment necessary for pinch and to increase the strength of grasp. At the distal end of this triplex framework lie multijointed appendages essential for any type of pinch or grasp more sophisticated than that of a lobster claw. The thumb has a highly mobile carpometacarpal joint but lacks a middle phalanx. Therefore, it has no proximal interphalangeal (PIP) joint and consequently no mechanical need for a lumbrical. Since the thumb has excellent coordination without a lumbrical, the lumbrical's function as a sense organ cannot be simply to coordinate finger movement. Mechanically the lumbrical is a deflexor of the PIP joint. Because lumbricals are richly endowed with muscle spindles, their passive stretch by contraction of the flexor digitorum profundus might both inhibit finger extensors and facilitate wrist extensors. Since each digit is unique, accurate mathematical and computer modelling of the hand must take into consideration this uniqueness.
The purpose of this study was to test the hypothesis that patients with mild primary hyperparathyroidism are protected against postmenopausal (PM) loss of cancellous bone architecture. To achieve this, we compared bone structure and turnover in iliac bone biopsies from three groups: 16 women with mild primary hyperparathyroidism (PHPT; 58.2 +/- 2.2 years, 11.5 +/- 1.7 years PM), 17 women with untreated primary osteoporosis (OP; 65.1 +/- 2.0 years, 17.2 +/- 2.3 years PM), and 31 healthy women (N; 59.8 +/- 1.4 years, 13.4 +/- 1.5 years PM). The bone formation rate was significantly higher in PHPT than in either OP or N, and not different between OP and N. Cancellous bone volume, total strut length, and indices of connectivity (node number, node to node strut length, and node to terminus ratio) were significantly lower in OP than in either PHPT or N but were the same or higher in PHPT than in N. Indices of disconnectivity were significantly lower in PHPT than in N, whereas they were the same or higher in OP than N. The data were also analyzed in subgroups matched by years PM with no changes in the results. These findings indicate that osteoporotic patients with normal bone turnover have low bone volume and microarchitectural deterioration, while patients with mild PHPT have normal bone volume and normal or greater trabecular connectivity despite higher bone turnover. These findings suggest that mild PHPT protects against the loss of cancellous bone structure that normally follows menopause.