Spinal Deformity in Adults and Surgical Treatment Advances

At times, lumbar curves with substantial degeneration are best treated with fusion to the sacrum, usually anterior and posterior. Posterior surgery includes bone grafting and fixation down to the sacrum and pelvis. Anterior surgery depends on the circumstances and may involve the lower two to four segments of the spine or all the lumbar segments. Of late, our preference is the use of large trapezoidal mesh cages with bone morphogenic protein (BMP) sponges. The extent of the surgery is dependent on many factors.

Recent Surgical Advancements
• Most recent advancements include improved fixation techniques to provide anterior column support in the distal (lower) lumbar spine and sacropelvic (sacrum/pelvis) regions. We have found that bicortical (a type of screw) S1 fixation and bilateral iliac fixation with screws measuring 60-70mm in length and 7.0 to 7.5mm in diameter provide excellent fixation of the sacrum and pelvis. Many failures have been noted when the sacral screws are not protected by iliac screws.

• Options for anterior column support include either femoral rings (a type of bone graft) or large trapezoidal mesh cages.

• Bone morphogenetic protein (BMP) plays an important role in these surgeries. Most common in anterior surgery (especially in the middle and lower lumbar spine) 8-12mg of BMP is applied to each level and to the cages. Bone graft is not used. BMP is also used:

Posteriorly -- If surgically addressing a lumbar curve using posterior fusion and instrumentation from T11 to the sacrum, just local bone graft (no iliac harvesting) and BMP may be used. This is "off label" use of BMP.

Anteriorly -- If surgically addressing the lower three to four levels, BMP sponges may be used to eliminate harvesting additional iliac bone graft. Use of BMP and cages at more than one level is "off label".

Many patients who undergo revision surgeries may have already had their ilium (iliac crest, hip bone) harvested on one or both sides. BMP helps to eliminate the need to take additional iliac bone and reduces morbidity (post-operative complications).

At this time, BMP's track record for anterior use is understood better than it is for posterior use. The best knowledge suggests that 8-12mg of BMP is needed for each anterior level and perhaps 40mg for each posterior level.

Benefits to Patients and Their Surgeons
It is hoped that advancements in treatment will improve outcomes and reduce the incidence of pseudarthrosis (failed fusion), surgical time, blood loss, pain, and complications.

Special types of catheters and IVs benefit patients and surgeons. Some patients do not have all of their surgery performed in one day. In fact, it is not uncommon for certain types of surgeries to be done five days apart. When this is the case, subclavian lines or multiple lumen subclavian catheters can be used to provide 24-hour access to a central vein (called 'central venous access'). Nutrition fed intravenously helps to reduce problems associated with weight loss between surgeries.

The incidence of pneumonia, deep venous thrombosis, and deep wound problems is low. Bowel immobility is the biggest problem a patient may encounter between surgeries. A great deal has been learned and experience gained in the use of multiple lumen subclavian catheters and parenteral nutrition (providing nutrition and calories through an intravenous line).

Anticipated Future Developments
• A better understanding of when patients can be treated with simply an anterior distal (lower) lumbar procedure as opposed to treating all of the lumbar segments anteriorly is anticipated. The anterior distal lumbar approach provides better exposure of L4-L5 and L5-S1 and does not disrupt the rib cage or diaphragm. The anterior procedure to treat all of the lumbar segments requires a chest/stomach incision called a thoracoabdominal approach.

• There is more to learn about BMP -- its limitations and applications. Spine surgeons are optimistic that the cost of BMP will decline to make it more affordable.

• Advancements in the development of smaller implants would benefit patients and surgeons. Implants need to be strong with components of elasticity and plasticity. If an implant is too large or bulky, it can make it difficult to decorticate (roughen) the bed under the instrumentation and the implant may be felt beneath the skin.

• In addition, a multicenter study is underway to gather information about the treatment of adult spinal deformity. This study, launched by the Spinal Deformity Study Group, will culminate in a database of information to help establish treatment guidelines and principles involving types of adult spinal deformity.

References
1. Eck KR, Bridwell KH, Ungacta FF, Lapp MA, Lenke LG, Riew KD. Analysis of titanium mesh cages in adults with minimum two-year follow-up. Spine 2000; 25(18): 2407-2415.

2. Lapp MA, Bridwell KH, Lenke LG, Baldus C, Blanke K, Iffrig TM. Prospective randomization of parenteral hyperalimentation for long fusions with spinal deformity: Its effect on complications and recovery from postoperative malnutrition. Spine 2001;26(7): 809-817.

3. Kuklo TR, Bridwell KH, Lewis SJ, Baldus C, Blanke K, Iffrig TM, Lenke LG. Minimum 2-year analysis of sacropelvic fixation and L5-S1 fusion using S1 and iliac screws. Spine 2001;26:1976-1983.