Osteoporosis is a systemic disease characterized by bone rarefaction caused by alterations in the micro-architecture as bone destruction prevails on the reconstructive phase in the physiological process of bone reorganization.

The risk of fractures is the most feared result of osteoporosis, a consequence that mainly strikes the spine, hip, and wrist bones. The spine, due to the weight it must support, is a ‘high risk’ bone segment. (1) Epidemiological data (2) confirm the importance of this complication in osteoporosis:

  • in Europe, 1 individual on 8 among 50 year olds complains of vertebral fractures;

  • besides the data is still more rele vant in individuals over 80 years of age. In this age group 1 wo- man on 3 and 1 man on 9 present bone lesions in the spine total- ling 300,000 individuals with se- rious vertebral alterations cau- sed by osteoporosis;

  • despite this only 1/3 of these patients are correctly diagnosed;

  • related costs are quite high, both in terms of direct costs and indi rect intangible costs (related to pain and distress). All this forms a social issue of considerable relevance.

BONE PHYSIOLOGY AND THE DISEASE

The bone is formed by a cortical region with a trabecular region located inside. The volume ratio between the two components is 4:1 in normal conditions, except in the spine, where the cortical/trabecular component ratio is 1:2 with a metabolic turnover that is over 8 in the trabecular region. The trabecular structure presents vertical bone elements that practically support the body weight, which is distributed on every vertebra and horizontal element that strengthens the former: it is the horizontal component that most suffers from osteoporosis and enables the vertical lamellae to press down, thus exposing the vertebra to the risk of fractures. Decisive factors that encourage osteoporosis are:

A) Genetic-biologica

  • Caucasian race is most exposed
  • smoke
  • fair hair and skin
  • hereditary
  • scoliosis and phosphate
  • premature menopause
  • a slight figure

B) Individual-environmental

  • alcoholism
  • physical inactivity
  • bad nutrition
  • diet rich in fibre

Age, sex and physical inactivity and highly relevant pathogenetic elements; the net difference of hormone levels (reduced oestrogen levels and even reduced levels of testosterone) during the postmenopausal phase explains how this disease that concerns the middle-aged and especially the very old. Osteoporosis is commonly distinguished in:

(A)Type 1 or postmenopausal, characterized by an increased turnover of bone reorganization; and,
(B)Type 2 or senile, whose decisive factor is the inadequate production of bone tissue (inadequate reconstructive phase).

The diagnosis is based on clinical signs and on the patient’s history, in other words on diagnostic investigations of the bone component (MOC), of biochemical markers and using consolidated radiological techniques such as routine X-rays of the spine, CAT scans and MRIs. In the spine osteoporosis involves: a) vertebral bone lesions; b) reduced stability of the spine itself; c) possible, though rare, consequen ces on adjacent nervous structu res (bone marrow, nerve roots, nerves); but, d) it is almost always the pain, with subsequent serious disablement, that alerts the patient to vertebral alterations.

TREATMENT

Preventive treatment plays a major role in the management and especially in the prevention of osteoporosis (3). Once bone damage has established itself with clear clinical signs, pain in particular, treatment can be summarized as described below.

1) Medical

(a) bed rest (with the risk of worse- ning the osteoporotic condition!)
(b) analgesics (at times not effective in relieving pain of vertebral origin)
(c) corsets (quite badly tolerated, they however considerably redu- ce the individual’s Quality of Life)

2) Surgical

“Open-heart surgery” is rarely re commended and anyhow only when there is neurological dama ge, which is, on the whole, quite an exceptional possibility, despi- te the importance of the bone damage that can be radiologi- cally detected.

3) Mini-invasive

This is vertebroplasty, or rarely kyphoplasty. It has attained a pla ce of relevance among therapeu tic possibilities available in re- cent years, as it is now a techni- cally consolidated method.

PERCUTANEOUS VERTEBROPLASTY

Percutaneous vertebroplasty is a mini-invasive therapeutic procedure that involves the injection, under radioscopic control, of biomaterial generally termed “cement”, directly into the vertebral body. Invented in France (4) in the ‘80s to treat compressive vertebral angiomas and then widely used both in Europe and in the US, it is now arousing considerable interest in Italy too. This procedure is well tolerated even by patients in poor general conditions and can also be performed in day surgery. The operation’s duration, generally from 20-30 minutes to 1-2 hours, varies depending on the number of vertebrae treated. Pain relief is often immediate, enabling the patient’s early mobilization (5). The technique consists in injecting acrylic cement (polymethylmethacrylate) into the vertebra by means of a needle introduced under fluorosco
DIRECTIONS, PATIENT SELECTION AND CONTRAINDICATIONS

The correct indications for the procedure influence the high percentage of expected good results and limit complications to the minimum. Patient selection - they are not merely individuals with osteoporotic lesions - must be accurate and performed both clinically and radiologically, marking out the level to be treated where clinical and radiological concordance is relevant. In fact besides osteoporosis, metastatic tumours involving bone lysis can alter the vertebrae and justify vertebroplasty (7), invasive vertebral angiomas and the localization of myelomatous cells (8). Indications for vertebroplasty as per the American College of Radiology. 1) Painful osteoporotic fractures (fractures that are refractory to medical treatment, with pain that does not respond to minor analgesics and requires the use of strong analgesics, with subsequent collateral effects; significant limitation of daily activities and of the quality of life). 2) Osteonecrotic fractures (Kűmmel’s disease). 3) Pain associated with osteolytic vertebral lesions such as benign tumours, malignant tumours and angiomas. 4) Fractures caused by unstable compression. 5) Multiple fractures with deformed vertebral alignment (kyphoscoliosis), where further vertebral collapses can compromise respiratory and gastrointestinal function or definitely alter posture when standing erect and walking. 6) Chronic traumatic fractures that are not consolidated and are unstable (pseudoarthrosis) or present cystic degeneration. The presence of intense persistent and disabling pain is however an essential factor in correctly recommending a mini-invasive procedure. The patient’s case history, physical examination and radiological investigations enable to distinguish between the pain caused by an osteoporotic or pathological fracture and that caused by common osteoarthrosis associated with disk degeneration. The pain’s onset is generally acute, spontaneous (when sneezing, coughing), lifting moderate weights or after a minor trauma. Pain is relieved by bed rest and worsened instead by movements such turning in bed or rising from a chair and by standing erect. During the acute phase the patient can localize the pain with greater accuracy, while the pain later tends to be more widespread. It is clinically quite important to rule out any nerve root involvement that requires other procedures and that however advices against vertebroplasty. A careful assessment of the radiological material produced will indicate or contraindicate the performance of vertebroplasty: It is essential that vertebral peduncles and the vertebral “wall” are intact.
MECHANISM OF ACTION - BIOMECHANICS

The mechanisms behind the effectiveness of vertebroplasty have not been described in detail as yet. Three possible theories that trigger the main symptom, ‘pain’, have been considered to date: a) thermal, b) chemical, and c) mechanical. a) It is in fact possible that heat developed by the exothermic reaction and produced by the polymerization of PMMA destroys nerve endings; hence a denervation procedure would have an analgesic effect (9). b) The MMA monomer’s liquid part is chemically active: hence an action in this sense could explain chemical denervation. c) Mechanical stabilization however seems to be the mechanism that most probably ensures an analgesic effect. Cement injected inside the vertebrae would consolidate microfractures, whose movement causes pain by exciting periosteal nerve endings, (the same occurs by immobilizing fractures in other sites). This stabilization depends on the volume and quality of cement injected (10). The optimal quantity for injection has yet to be finally established; anyhow a case by case evaluation is required, applying the rule that overfilling is not always necessary to obtain good clinical results.

TECHNIQUE

The patient‘s position: the patient must be made very comfortable. This will enable him to easily endure a procedure that does not take very long. With the exception of surgery on the cervical rachis, the patient will be prone; hence to make this position easier to endure the bed surface must be soft and cushions must be placed under chest, sternum and pelvis to ensure adequate abdominal movement while breathing. Anaesthesia: the procedure requires the presence of the anaesthetist and total patient monitoring. Anaesthesia is however local and general sedation is also administered. Approaches: the choice of approach depends on the levels of the vertebrae to be treated. The transpeduncular approach through the lumbar vertebrae is the safest anatomical route to access the vertebral body. (See figure) Complications: the incidence of collateral effects and complications is quite low (1-2% in osteoporotic fractures; 3-10% in tumours). The choice of patient and indications must be carefully evaluated (11) and a detailed informed consent form must be signed. This form should describe procedure, expected results and risks involved. However this is a reasonably safe procedure in expert hands.

CONCLUSIONS

Vertebroplasty is a mini-invasive method, the choice treatment for cervical pain, chest pain and backache caused by vertebral collapses of osteoporotic origin. Besides, the procedure is also recommended in other pathological conditions such as metastases, invasive angiomas and myelomas. Clinical results achieved are rather interesting (12). Most patients who were weakened or disabled prior to the procedure could move painlessly once again and a considerable improvement was noticed in their quality of life. Social costs too are doubtless economically interesting. Vertebroplasty must be considered an extremely relevant advancement in modern medicine as it offers those who suffer and those whose daily activities are limited by a common disease such as osteoporosis valid aid in managing an unfortunately frequent complication such as vertebral collapse with acute pain that is extremely difficult to control.

Prof. Mauro Porta
Direttore Centro del Dolore e Cefalee
Istituto G. Galeazzi - Milano