Orthopedics - Oleksa A.P. 2006

Metabolic Bone Diseases
Hyperparathyroidism (parathyroid osteodystrophy, osteitis fibrosa, von Recklinghausen's disease)

Children of both sexes over the age of 10 are most commonly affected.

Hyperparathyroidism is caused by an Adenoma of the Parathyroid glands (in 80–90% of cases), or more rarely, by their hyperplasia. This condition results from excessive parathyroid hypersecretion, typically driven by an adenoma in a single parathyroid gland.

Heredity plays a significant role in the onset of the disease. The literature describes over two dozen cases of familial hyperparathyroidism (Zhukovsky M.A. et al., 1971).

Increased production of parathyroid hormone leads to Calcium and phosphorus Metabolic Disorders. The hormone acts by inhibiting the tubular reabsorption of phosphorus in the Kidneys, which results in enhanced urinary excretion of phosphates and a decreased serum phosphorus concentration.

To restore equilibrium, calcium is mobilized from the bones in the form of phosphate compounds. The rapid and excessive elimination of phosphates from the body via urine leads to an elevated amount of calcium—released from the bones—in the Blood, its excretion in the urine, and its deposition in Tissues. Due to this increased release and excretion of calcium, urolithiasis sometimes develops (Crawford A., Hamblen D.L., 1990).

It has been proven that parathyroid hormone activates osteoclasts, promotes local acidosis, and inhibits The activity of alkaline phosphatase (Zhukovsky M.A. et al., 1971).

Based on the dominant Clinical Features, primary hyperparathyroidism is classified into bone, renal, visceral, and mixed forms.

The Clinical presentation of primary hyperparathyroidism is characterized by polymorphic changes in both Internal Organs and bones. Determining the onset of the disease is extremely difficult because early symptoms are subtle. Patients may complain of polyuria and polydipsia, pain in the Muscles, joints, and bones, general weakness, fatigue, and mental depression.

Alterations in blood chemistry and the suppression of neuromuscular excitability lead to Muscle weakness and bone pain, particularly in the lower extremities and spine. This causes rapid fatigue and general weakness. Atony of the smooth Muscles of the gastrointestinal tract results in anorexia, nausea, vomiting, and abdominal pain.

Bone pain may be intermittent, but it appears even after minor exertion. Radiographic examination reveals rarefaction throughout the Skeleton, with a loss of normal bone density and thinning of the trabeculae and cortical layer. An early radiological sign is irregular subperiosteal erosion and cysts on the middle Phalanges of the hand (Fig. 95). In later stages, single- or multilocular cysts resembling soap bubbles appear, along with Changes in the spine, pelvis, and Skull (Fig. 96).

Bone changes are responsible for frequent fractures that occur spontaneously or following minor trauma. Consequently, clinical and radiological examinations reveal deformations in both the long bones and the spine. The spine collapses, leading to increased Kyphosis, which reduces the patient's height, while the skull enlarges due to The formation of intraosseous cysts.

The increased excretion of calcium and phosphorus in the urine initially manifests as polyuria and a reduced urinary concentration capacity, while in the later stages, Nephrolithiasis and nephrocalcinosis gradually develop, ultimately leading to renal failure.

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Fig. 95. Bone resorption and cysts of the proximal phalanges of the hand.

Fig. 96. Primary hyperparathyroidism with involvement of the cranial bones (Vaswani A., Dee R., 1997).

Calcium salt deposition may also occur in tendons, Salivary Glands, and other tissues.

The mainstay of Diagnosis is the laboratory detection of hypercalcemia, hyperphosphatemia, hypercalciuria, and hyperphosphaturia, as well as a significant elevation in alkaline phosphatase levels (Table 3).

The most accurate indicator of parathyroid function remains the determination of ionized calcium. In clinical practice, the Sulkowitch test is frequently performed; it is based on the principle that a healthy body excretes no more than 30% of administered calcium in the urine, whereas in hyperparathyroidism, this excretion rises to 70–90%.

The Hamilton-Schwartz test is sometimes used, which relies on changes in blood calcium levels in laboratory animals following the administration of blood from a patient with hyperparathyroidism.

A calcium tolerance provocative test can also be used to diagnose hyperparathyroidism.

Primary hyperparathyroidism must be differentiated from secondary hyperparathyroidism (Fig. 97), which is a compensatory response of the parathyroid glands to decreased blood calcium levels in various diseases. Renal Rickets, De Toni-Debré-Fanconi Syndrome, and renal acidosis with Osteomalacia are characterized by acidosis, which does not occur in primary hyperparathyroidism. Furthermore, blood calcium levels in these conditions are normal, and urinary calcium excretion is reduced, while phosphorus levels remain unchanged.

Occasionally, Recklinghausen's disease must be differentiated from Fibrous Dysplasia of bone, which shares similar clinical and radiological features. Fibrous dysplasia typically affects a single bone and presents with pigmented Skin spots whose distribution corresponds to the segmental bone lesion, as well as premature Puberty.

Unlike hyperparathyroidism, serum levels of calcium, phosphorus, and alkaline phosphatase remain within normal limits in fibrous dysplasia, Gaucher disease, and Niemann-Pick disease, serving as a basis for Differential diagnosis.

In Gaucher disease, Bone Marrow aspirates contain Gaucher Cells. In Niemann-Pick disease, the Spleen and Liver are invariably enlarged, and bone marrow aspirates reveal "foamy cells."

Thus, the Diagnosis of Primary hyperparathyroidism is generally straightforward, except in the Cytology/cytology/16.html">Early stages of the disease when clinical manifestations are vague.

Treatment. Once the diagnosis is confirmed, the only reliable treatment for hyperparathyroidism to date is the surgical removal of an adenoma or hyperplasia of the parathyroid glands. Following surgery, calcium and phosphorus METABOLISM normalizes, and bone changes gradually reverse, leading to increased bone density and strength. Occasionally, transient tetany may occur postoperatively due to hypocalcemia, which resolves over time. In such cases, calcium supplements are prescribed, and Procedures such as subcutaneous bone implantation have been attempted. Our observations indicate that bone transplantation has only short-term efficacy, which can be attributed to the encapsulation of the bone graft.

Fig. 97. Secondary hyperparathyroidism. Cystic and sclerotic changes in the vertebral bodies (Matzen/Matzen, 1990).

Table 3. Characteristic biochemical, histological, and radiological changes in disorders accompanied by bone demineralization and remodeling (after Brühl W., 1969)