Osteoporosis

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Surgical treatment of osteoporosis is still not widely accepted by orthopedic surgeons, nor well known among the medical community at large. However, recently, it has been gaining support for two main reasons. The first is that more in-depth studies, which are detailed below, have shown that osteoporosis is not an innocent disease characterized by minor complications and disabilities, but a serious health problem that can create devastating complications with substantial morbidity and mortality. The second reason is the advancement of medical knowledge and technology, which allows the use of more sophisticated instrumentation and makes it possible to operate successfully on high-risk patients of advanced age who no longer accept physical conditions limiting their life enjoyment.

The extent of disability and the socioeconomic consequences associated with osteoporosis are well known through widely cited publications [24, 94, 112]. It is not the scope of this paper to review this aspect of osteoporosis. However, it is worth highlighting some pertinent statistics regarding the magnitude and implications of osteo-porotic vertebral compression fractures (OVCF) in order to emphasize the need for a more specific treatment. OVCF is the most common fracture that may occur after minimal trauma (e.g. bending, turning, etc), or even in the absence (silent) of any obvious trauma [25].

The estimated incidence of OVCF in European Union Member States is 438,700 clinically diagnosed vertebral fractures (117 per 100,000 person-years) [25], while the US epidemiological databases give an annual rate of 700,000 cases [111].

The average duration of hospitalization ranges from 8 to 30 days [111].

The reported periods of disability for cases of OVCF required for bed rest are 25.8 days for the lumbar region and 12.6 days for the thoracic region. The periods of disability required for limited activity are 158.5 days and 73.6 days respectively. Whereas the figures for hip fracture are 21.6 days for bed rest and 101.5 days for limited activity [37].

Apart from physical impairment incurred by the OVCF [87, 126], these patients also experience a substantial deterioration in quality of life and a cascading of psychoso-

cial disorders, such as sleep disturbance, increased depression, lower self-esteem, increased anxiety, diminished social poles and increased dependency on others [127].

The overall mortality rate also appears to be equivalent to hip fractures. A prospective study of 9575 women, followed over 8 years, demonstrated that patients with OVCF have a 23-34% increased mortality rate when compared to patients without OVCF [69]. This study echoes the findings of Cooper et al. [25], who demonstrated in a retrospective study that the 5-year survival rate in patients with OVCF is significantly lower than the expected normal survival rate (61 vs 76%), and almost comparable to the 5-years survival rate after hip fracture. However, in hip fractures, the excess mortality rate occurs within 6 months of the fracture event, whereas in OVCF survival declines steadily after the fracture [25]. Most common causes of death in patients with OVCF are pulmonary problems caused by chronic obstructive pulmonary disease (COPD) and pneumonia (hazard ratio 2.1) [69]. Lung function (FVC, FEV1) is significantly decreased in patients with thoracic and lumbar fracture. It has been estimated that one OVCF may result in 9% loss of forced vital capacity (FVC) [82, 121, 122].

Eighty-five percent of cases of radiologically diagnosed OVCF are associated with back pain, which in the majority of patients is expected to subside within 2-3 months [34]. However, it has been postulated that in one-third of patients, this pain remains as chronic pain, with varying degrees of physical disability [29]. Several reports also indicate that patients with OVCF are at increased risk for subsequent fractures [68, 84, 114]. Most cases of OVCF are wedge compression fractures (type A1), creating varying degrees of kyphotic deformity of the spine, usually not associated with neurological deficit. These fractures are manageable either conservatively (braces, corsets, analgesics and antiresorptive osteoporotic drugs such as calci-tonin and bisphosphonates, or parathyroid hormone, apparently the most effective antiosteoporotic drug) [22, 70, 88], or surgically by means of minimally invasive surgery (vertebroplasty, balloon kyphoplasty). These procedures have been recently introduced in the treatment armamentarium for OVCF as a more effective treatment [42, 83].

According to a study by Parfitt and Duncan, published in 1982 [101], spontaneous crush fractures in osteoporotic patients do not result in spinal cord compression requiring decompressive surgery. However, several reports have since appeared in the literature highlighting the fact that spontaneous osteoporotic fracture with serious spinal cord compression and variable degrees of neurological deficit do occur [6, 8, 26, 27, 63, 71, 72, 75, 77, 90, 97, 98, 118, 119, 125, 132].

There are five main reasons for operating on osteo-porotic spines:

1. Acute or subacute osteoporotic fractures that can be corrected or stabilized by minimally invasive surgery (ver-

tebroplasty or balloon kyphoplasty)

Kyphosis Patient
Fig. 1 A patient with painful kyphosis. Could this deformity have been prevented?

2. Conditions requiring spinal instrumentation, such as extensive laminectomy, which may destabilize an osteo-porotic spine

3. Prevention of severe kyphotic deformity developing from osteoporotic fractures (Fig. 1)

4. Established painful deformities (kyphosis/scoliosis), and

5. Symptomatic neurocompression caused by osteopo-rotic fractures

Surgical treatment

Anterior decompression was accomplished through an anterior approach in 15 patients (8 for painful deformity and 7 for neurological deficit). Anterior stabilization alone was achieved by means of a Kostuik rod: n=1, a Kaneda device: n=4, or a plate: n=1. Posterior stabilization was performed in three cases, and combination of anterior Kaneda and posterior instrumentation (Varigrip hook) in another six cases. Anterior reconstruction was achieved by means of bone graft in four cases (femoral ring allo-graft: n=2 and ribs: n=2), and Harms titanium cages filled with bone graft in 11 cases. A posterior approach alone was used in 11 cases, and consisted of either wide laminec-tomy and stabilization (eight cases), or indirect reduction and stabilization (three cases). More specifically, instrumentation consisted of multisegmental fixation with either transpedicle screws (bone cement augmentation n=2; triangular technique n=2) or laminar claws (Varigrip) or a combination of the two.

Three patients who had serious co-morbid diseases were treated with morphine pump. One had a partial parapare-sis and the other two intractable painful deformities.

Outcomes

The patient with complete paraplegia never recovered (Fig. 2), whereas patients with Frankel B, C, or D improved by two grades. All patients with serious neurolog-

Review of a series of 29 cases

A review recently conducted by the present authors of 29 patients treated for serious musculoskeletal spinal and neurological complications from osteoporosis of the spine shows how serious the condition can be and how important it is to maintain surgery as a treatment option. The patients were managed surgically between January 1994 and January 2001 at the University of Texas Medical Branch at Galveston, at the University of Crete, Heraklion, and at the National University of Greece in Athens.

Fifteen patients were treated for severe neurological compromise, ranging from paraplegia to paraparesis (Frankel A: n=1, Frankel B,C and D: n=14) and 14 for intractable back pain complicating kyphoscoliotic osteo-porotic deformities. Acute burst fractures were observed in five patients and were associated with serious neurological complications (Frankel B in four and Frankel A in one). Ten patients suffered from wedge compression fractures, two developed acute onset of symptoms, and in the remaining eight, the neurological deterioration was gradual. (The neurological deficit grading was Frankel B in two, with the rest ranging between C and D.)

Vertebrae Double Wedge Fracture
Fig. 2 Osteoporotic pathological fracture of T6, resulting in severe kyphosis and rapid progression of neurological deficit to complete paraplegia (a). The patient failed to recover after anterior decompression and stabilization (b)

Fig. 3 Dislodgment of anterior instrumentation construct in an osteoporotic L1 fracture (a). This resulted from poor application of instrumentation principles in an osteoporotic spine. It was successfully revised using anterior and posterior multisegment fixation constructs (b)

Fig. 3 Dislodgment of anterior instrumentation construct in an osteoporotic L1 fracture (a). This resulted from poor application of instrumentation principles in an osteoporotic spine. It was successfully revised using anterior and posterior multisegment fixation constructs (b)

Table 1 Outcomes of surgery for spinal cord neurocompression and painful deformities

Procedure

Serious neurological deficit"

Painful deformities (kyphosis/scoliosis)

Combined

Table 1 Outcomes of surgery for spinal cord neurocompression and painful deformities

Procedure

Serious neurological deficit"

Painful deformities (kyphosis/scoliosis)

Combined

Total

Improvement

Failure

Total

Success

Failure

Total

Success

Failure

Anterior decompression + graft

l

ó/l

1/l

s

5/s

3/s

15

11/15

4/15

or cages

Anterior stabilization

3

2/3

1/3b

3

0

3/3c

ó

2/ó

4/ó

Posterior stabilization

-

-

-

3

3/3

0

3

3/3

0

Combined

4

4/4

0

2

2/2

0

ó

ó/ó

0

Posterior decompression,

3

3/3

0

-

-

-

3

3/3

0

indirect reduction + stabilization

Posterior decompression +

4

3/4

1/4

4

2/4

2/4

ä

5/s

stabilization

Morphine pump

1

0

1/1

2

1/2

1/2

3

1/3

2/3

a "Serious neurological deficit" indicates Frankel B-D. "Improvement" denotes patients' neurological status improved by at least two Frankel grades. The patient with morphine pump deteriorated from Frankel D to Frankel B

b One patient with complete paraplegia never recovered c Two patients developed junctional kyphosis. One was successfully corrected by supplementing posterior instrumentation. The other healed in a kyphotic deformity with residual pain. Complete dislodgement of instrumentation occurred in the third patient, who was revised successfully through a combined approach.

a "Serious neurological deficit" indicates Frankel B-D. "Improvement" denotes patients' neurological status improved by at least two Frankel grades. The patient with morphine pump deteriorated from Frankel D to Frankel B

b One patient with complete paraplegia never recovered c Two patients developed junctional kyphosis. One was successfully corrected by supplementing posterior instrumentation. The other healed in a kyphotic deformity with residual pain. Complete dislodgement of instrumentation occurred in the third patient, who was revised successfully through a combined approach.

ical deficit underwent anterior decompression. Pain improved substantially in all patients, as well as in the patients who underwent revision surgery. Two of the patients in the deformity group who underwent anterior decompression and anterior stabilization developed junc-tional kyphosis, which was corrected by indirect reduction in hyperextension and stabilization with posterior instrumentation. In one patient, complete dislodgement of a cage and an anterior device occurred soon after surgery, and responded well to revision surgery (Fig. 3). In the pa tient with paraparesis, morphine pump was successful as a pain management modality; however, his neurological status deteriorated and the patient died after a few months.

A morphine pump substantially improved the pain in one patient with painful deformity and failed in the other patient (Table 1).

Fig. 4 Acute burst fracture in a patient on chronic use of steroids, who sustained the fracture after a minor trauma (bending over and lifting a heavy object). The onset of severe paraparesis was late, gradual and crippling. Neurological status responded successfully to posterior decompression and stabilization, but the treatment failed to correct the deformity and the patient remained with severe back pain

Fig. 4 Acute burst fracture in a patient on chronic use of steroids, who sustained the fracture after a minor trauma (bending over and lifting a heavy object). The onset of severe paraparesis was late, gradual and crippling. Neurological status responded successfully to posterior decompression and stabilization, but the treatment failed to correct the deformity and the patient remained with severe back pain

Discussion

With the increasing size of the elderly population (people at risk), it is expected that the rate of osteoporotic vertebral fracture and resulting neurological complications will rise dramatically.

Acute kyphotic deformity as a result of OVCF is not usually associated with neurological deficit, but may continue to remain as a painful crippling condition requiring major surgical intervention (Fig. 1). The type of OVF that can cause neurocompression results from either acute crush fracture [77, 98, 102] (Fig. 4) or delayed collapse of an antecedent wedge fracture that leads to retropulsion of a vertebral body fragment and contribution to progressive kyphotic deformity [71, 75, 97].

The reported time period from the original injury to clinical manifestation of neurocompression varies between 1 and 18 months [8, 71, 75]. The cord is compromised either by the severity of the kyphotic deformity or by retropul-sion of a posterior wall fragment [8, 63, 71, 75, 97]. The postulated mechanisms of delayed vertebral collapse are attributed to either bone ischemia and necrosis [13, 18, 71, 75], or pseudarthrosis [60]. Apparently, it is a combination of both these factors [71, 75]. Repeated microtraumas have been postulated as the causative factor for pseudarthrosis [75], which produces an unstable kyphotic spine and severe pain [75].

Neurological deficit can range from acute paraplegia (usually after an acute crush fracture) [98, 102] to delayed onset of insidious paralysis that gradually deteriorates to severe paraplegia [69, 73]. The latter phenomenon is usu

Fig. 5 Correction of a rigid painful post-fracture kyphoscoliotic deformity by means of anterior and posterior instrumentation

Causal Tree Diagram
Fig. 6 Principles of surgery of osteoporotic vertebral fracture with neurological deficit or severe painful kyphotic-scoliotic deformity. A,B,C signify sequential steps for each approach

ally associated with delayed vertebral collapse and progressive kyphotic deformity [75]. Within this context, therefore, it is not unreasonable to entertain balloon kypho-plasty, a recently introduced minimally invasive surgery, as a preventative intervention for progressive kyphotic deformity (Fig. 1).

Table 2 Reported cases of severe neurological deficit caused by osteoporotic vertebral fractures

Authors

No. of cases

Neurological status

Type of fracture

Treatment

Results and remarks

Salomon et al. 1

1988 [119]

Kaplan et al. 3

Arciero et al. 2

Shikata et al. 7

1990 [125]

Kaneda et al. 22

Heggeness 9

Tanaka et al. 1993 [132]

Korovessis et al. 1994 [77]

Courtois et al. 1998 [27]

14 10

Spastic paraparesis

Neurological deficit

Paraparesis: acute onset 1, delayed onset 1

Delayed paraparesis

Gradual onset incomplete paralysis

Gradual onset of neurological symptoms

Delayed conus medullaris syndrome

Delayed cord compression; paraplegia 1

Gradual onset: paraplegia 1, paraparesis 3, leg weakness 2, sphincteric dysfunction 2

Gradual late paralysis

Gradual progression of leg weakness

Cauda equina syndrome

Acute onset with gradual deterioration

Acute onset of complete paraplegia

Gradual onset of severe paraparesis

Frankel D: 7, Frankel C: 3; late onset: 9, acute onset: 1

Wedge fracture with acute retropulsion

Burst with retropulsion Acute burst fracture 5 burst Fx, 5 wedge Fx

Combined posterior and anterior approach

Anterior decompression Posterior decompression

Wedge fracture with de- Anterior decompression layed bone retropulsion

Delayed collapse with bone retropulsion

L1 burst fracture

Burst fracture with progression

Vertebral crush Fx

Delayed collapse with bone retropulsion

Progressive loss of vertebral height; retro-pulsion of fragments; progressive kyphosis

L2 Fx with osteonecrosis

Wedge compression

Crush with retropulsion

Wedge fracture with delayed retropulsion

Burst with retropulsion

Anterior decompression and fusion

Anterior or posterior or combined approach

Surgery: 3

Conservative: 3

Anterior or posterior decompression

Combined anterior and posterior approach

Spondylectomy

Conservative

Anterior cord decompression

Surgery

Complete recovery

Spontaneous Fx, no trauma

Nearly complete recovery

Substantial improvement

Excellent

Benign appearing compression Fx may progress to serious situation

Restoration of vesi-corectal function

6 recovered, 1 (with paraplegia) died

1 recovered, 1 improved, 1 unchanged

1 improved,

2 unchanged

Recommend transpedicular posterolateral decompression

Recovery

Imaging failed to diagnose oseteonecro-sis. Diagnosis made from the biopsy.

Excellent

Died

Excellent

8/10 survived, 6/10 improved, 1/10 deteriorated

Based on our findings and the experience of others, we have shown that posterior instrumentation alone, after wide laminectomy, can improve neurological deficits even in seriously spinal cord-compromised patients in the acute fracture where indirect reduction of kyphotic deformity is feasible. However, for rigid curves (Fig. 5), a combined anterior and posterior approach seems a more appropriate treatment. For an experienced surgeon, anterior decom pression and stabilization with or without posterior stabilization can achieve excellent results in terms of neurological decompression and correction of painful deformities [22]. Anterior decompression and stabilization can also be achieved through a posterior or posterolateral translaminar approach.

Fig. 6 outlines the techniques of surgical management of OVF when the spinal cord is compromised, and Table 2

Fig. 7 Paraparesis after spontaneous osteoporotic fracture (a), corrected by anterior decompression and reconstruction (b)
Fig. 8 Pathological osteoporotic fracture with complete restoration of neurological deficit after anterior decompression, iliac bone graft and Kaneda stabilization

summarizes the published reports of serious neurocompression complicating osteoporotic fractures.

Surgical approach

Through an anterior approach, decompression of a retro-pulsed bone fragment can be easily and safely performed. Reconstruction and fusion can be achieved either by femoral ring bone allograft, rib struts, iliac bone, cages filled with bone chips, or bioactive ceramic [71] (we do not use methylmethacrylate as a reconstruction material advocated by others) [6]. Stabilization can be accomplished using a Kaneda device or similar rigid anterior in-

Fig. 9 a Anterior decompression and reconstruction with femoral ring bone graft and posterior stabilization. b Anterior decompression and reconstruction with titanium mesh cage filled with bone chips; stabilization was obtained though a combined anterior and posterior long multisegmental stabilization construct strumentation (Fig. 7, Fig. 8). Because screw holding grip is incomplete in osteoporotic bone, we advocate that the screw should stabilize the contralateral vertebral body cortex. Stabilization can also be obtained through a posterior approach (Fig. 9). Alternatively the surgeons could elect first to stabilize the spine posteriorly and, in the same sitting, proceed with an anterior decompression [119].

Anterior cord decompression can also be performed through a posterior transpedicle or posterolateral approach. In general, many surgeons who are more familiar with the posterior approach prefer this method, which also avoids the need for sectioning the diaphragm - especially advantageous in elderly patients with serious pulmonary problems [75, 125]. Through this approach, cord decompression can be achieved either by:

- Partial posterior vertebrectomy and bone grafting [75]

- Driving forward the retropulsed fragment by gentle direct tapping [125], or

- Performing a vertebrectomy to accomplish shortening and decompression of the spinal cord [118]

The spine is then stabilized through a posterior instrumentation, preferably by using transpedicular screw fixation two to three levels above and below the decompression. The only technical complication reported with this approach is dural tear (14%) [75]. Laminectomy, as a standalone procedure, should be rejected, because it does not deal with the anterior cord compression, and further deterioration of neurological deficit from progressive kyphotic deformity has been observed [73].

Fig. 10 Junctional kyphosis after anterior instrumentation (a), corrected by posterior instrumentation combining screws and hooks(b)

Options for instrumentation

Hardware loosening or cut-out with dislodgment of instrumentation construct are the most serious technical complications when operating on osteoporotic spines. To avoid this, the surgeon should be aware of certain well-established surgical principles when instrumenting osteo-porotic spines, as suggested by Hu [66]:

1. Try to avoid the use of hooks or screws as the sole fixation device.

2. Avoid ending the instrumentation within kyphotic segments [66] (Fig. 10) to prevent junctional kyphotic complications [66, 86].

3. Use multiple sites of fixation to dissipate stresses and therefore decrease stresses at any site [66] (Fig. 9b, Fig. 5). Similarly, the excessive forces on the instrumentations, can be sufficiently dissipated by combin-

Fig. 11 Pathological fracture with severe delayed neurocom-presion (a), treated by means of anterior decompression and reconstruction with rib strut graft (b). c Posterior stabilization with screws and Varigrip claws ing anterior and posterior surgical approaches and instrumentation [14]. 4. Accept a lesser degree of deformity correction (Fig. 11), in order to avoid hardware pull-out from excessive corrective forces [66].

And, finally, one should keep in mind that fixation may not be feasible!

As an ultimate salvage approach one may consider a morphine pump, as the last attempt to control musculoskeletal pain in moribund patients.

In relation to point (1) above, there are a number of considerations to bear in mind. Laminar hooks are considered to be more resistant to posteriorly directed forces, because laminar bone is more cortical than cancellous and will therefore have been affected by osteoporosis [21]. Hooks in a claw configuration spanning two vertebral levels can augment the holding grip of the construct. Experimental work indicates that transpedicular screw axial pull-out is correlated to the vertebral bone mineral density [21, 58, 99, 131]. Triangulation of pedicle screws apparently resists axially directed screw pull-out [54, 55]. Augmentation of transpedicle screw fixation in osteoporotic patients using polymethylmethacrylate has been accepted as a sound technical principle [22, 85, 96, 131]. A combination of pedicle screw and laminar hooks will provide the greatest resistance to pull-out forces [7, 17, 58, 61, 92] (Fig. 11). Hu thinks that sublaminar wire fixation of spinal rods is a sound surgical principle in osteoporotic spine [66]. Although sublaminar wires pose a potential risk for neurological complications, they are ideal because the multiple sites of wire fixation decrease the stresses generated at points of fixation [66].

Osteoporosis: conclusion

In conclusion, several caveats deserve to be highlighted here. Osteoporotic fracture of the spine is not always an innocent occurrence, as most people are led to believe, but

can give rise to serious and crippling neurological complications and painful deformities as well. Surgery in these cases is apparently the sole alternative approach, and may turn out to be a formidable task. However, the clinician who is armed with knowledge of the best options in surgical treatment can effectively and safely manage the problem, which is anticipated to be seen more frequently in the near future. The aging population should be rewarded with the enjoyment of life without pain and disabilities.

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