Yan Wang, Oheneba Boachie-Adjei and Lawrence Lenke (eds.)Spinal Osteotomy10.1007/978-94-017-8038-4_20

20. Revision Surgery Following Spinal Osteotomy

Greg Anderson¹ and Alex Johnson¹

(1)

Department of Orthopaedic Surgery and Neurological Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States

Greg Anderson

Email: greg.anderson@rothmaninstitute.com

20.1 Introduction

Spinal deformities, including both sagittal and coronal plane deformities, may lead to debilitating symptoms. Patients suffering from significant spinal misalignment may present with pain, loss of functional capacity, muscle fatigue, aesthetic concerns, deteriorating self-image, and reduced ambulatory capacity. In adults, deformities of the sagittal plane are most commonly associated with symptoms severe enough to warrant major reconstruction of the spinal column. There are many causes of sagittal malalignment including ankylosing spondylitis, lumbar degenerative disease, posttraumatic kyphosis, deterioration of an old idiopathic scoliosis, and deformity adjacent to a prior spinal fusion [1–3]. Since 1945, when Smith-Peterson et al. [4] first described a vertebral osteotomy procedure, osteotomies have increased in prevalence and evolved in complexity to provide an effective means of correction for most rigid spinal deformities. Many spinal osteotomy techniques have been described including Smith-Peterson osteotomy (SPO) [1, 4–6], pedicle subtraction osteotomy (PSO) [1, 2, 5, 6], cervical extension osteotomy [1, 7], vertebral column resection (VCR) [1, 6, 8], and the anterior/posterior osteotomy procedure [9, 10]. Each type of osteotomy techniques has specific indications. Careful planning is required to determine the optimal approach for each patient. Osteotomy procedures, used alone or in combination, provide powerful tools for the treatment of complex and rigid spinal deformities. Spinal osteotomy procedures are generally complex and invasive procedures that involve substantial risks which must be weighed carefully against the potential benefits in each clinical situation.

Although much has been written about the topic of spinal deformity correction, the topic of revision osteotomy surgery remains a sparsely studied area of spinal surgery [11–14]. The potential indications for revision osteotomy surgery are broad and might include insufficient or overcorrection, loss of fixation, pseudarthrosis, adjacent level degeneration, neurologic deterioration, and progressive or unacceptable deformity [11, 15]. The existing literature on osteotomy revision is most illuminating in two broad areas: acute neural deficits and failed anatomical correction. Additionally, there are a myriad of nonspecific reasons for revision surgery such as surgical site infection or wound complications but will not be the focus of the current manuscript. This chapter will review the available literature regarding revision spinal osteotomy surgery and will discuss treatment strategies to consider when faced with a complex osteotomy revision procedure.

20.2 Assessment of Outcome in the Post-Osteotomy Patient

The goal of a spinal osteotomy is to correct a significant and rigid deformity of the spinal column. Clinically, an osteotomy is generally intended to improve standing or sitting posture, alleviate pain, and improve biomechanical functioning of the patient. Unfortunately, the desired spinal correction is not always achieved or maintained over time. Therefore, postoperative surveillance is necessary following major deformity correction.

A variety of clinical tools have been utilized to assess outcome following major spinal deformity correction. These tools help to objectify both functional status and patient satisfaction and allow comparison between the preoperative and postoperative status of the patient. Examples of health-related quality of life (HRQL) tools include the Oswestry Disability Index (ODI) and the Scoliosis Research Society Scoliosis Patient Questionnaire (SRS-22 or SRS-24). Patients with poor or declining scores should be carefully assessed to identify the underlying cause of the dysfunction. In cases where the primary cause of dysfunction is related to poor sagittal balance, additional surgery may be considered in order to improve the patient’s functional status and quality of life.

Overall outcome assessment for a post-osteotomy patient requires a combination of clinical factors, physical exam findings, and radiographic parameters. Revision surgery is almost universally a major operative procedure, so a careful assessment of the patient’s general health and ability to tolerate surgery are required. The surgeon and patient must enter into a detailed discussion of the treatment goals, therapeutic options, and risks of surgery. This frank discussion can help the patient to set realistic expectations when major revision surgery is contemplated.

When assessing a spinal deformity patient, full length (36”) radiographs including the femoral head should be obtained and the relevant spinal deformities including the spinopelvic parameters should be determined. A strong correlation has been documented between HRQL scores and sagittal balance. Various measures have been described to evaluate the sagittal balance of the spinopelvic region including the T1-spinopelvic inclination (T1-SPI), sagittal vertical axis (SVA), pelvic tilt (PT), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and lumbar lordosis to pelvic incidence (LL–PI) mismatch. The target for these parameters as reported in various studies is in the range of T1-SPI < 0°, SVA < 4 cm, PT < 20°, and LL–PI ± 10° [13–16]. Recent literature has placed special emphasis on the SVA and LL–PI measurements which are crucial to the planning of an osteotomy procedure.

20.3 Indications for an Osteotomy Revision

Although a corrective spinal osteotomy can potentially produce a major positive impact for a patient afflicted with severe, rigid spinal deformities, the risk of complications with this type of surgery is high [2, 3, 16, 17]. There are several reasons why additional surgery may be required following an osteotomy procedure. These include acute neurologic deficits, failed anatomical correction, loss of fixation, pseudarthrosis, or adjacent level degeneration leading to further spinal deformity. Acute neurologic deficits are generally recognized in the early postoperative period and may necessitate a rapid return to the operating room for additional surgery if a correctable cause of the deficit is felt to be present. Buchowski et al. [2] reported a neurologic deficit rate of 11.1 % in 108 patients undergoing complex osteotomy surgery. Three patients with deficits were identified on wake-up test, four patients were found to have deficits on the immediate postoperative neurological exam, and five patients developed deficits during the hospital stay. All of the deficits involved a single lower extremity. Patients felt to have a correctable cause of the deficit were treated by additional decompression of the neural elements with widening of the spinal canal at the osteotomy site. Six of the nine patients treated with revision surgery suffered no permanent deficit. Similar studies have also reported a benefit for early revision surgery in osteotomy patients experiencing an acute postoperative neurologic deficit that was believed to be caused by compressive spinal pathology at the osteotomy site [3, 16].

A failed anatomic correction presents a complex clinical situation requiring an individualized treatment strategy. A thorough understanding of the deformity, status of the fusion, and integrity of any existing spinal instrumentation, as well as assessments of the patient’s general health are required prior to formulating a treatment plan. Mathematical planning tools for osteotomies have been developed [18] which can help to identify the goals for correction to achieve ideal spinopelvic parameters [13–19]. Recent studies have demonstrated that spinopelvic parameters are the best predictor of patient satisfaction after an osteotomy procedure [13–16]. The goal of every osteotomy should be to achieve spinopelvic balance, which will allow energy efficient ambulation by placing the trunk and head over the pelvis and lower extremities. Patients that fall well outside the normal spinal balance are forced to use compensatory mechanisms to maintain balance, which produces a severe impact of quality of life. Poor quality of life due to loss of spinopelvic balance is a reasonable indication for revision surgery. Additional considerations include patient-specific anatomic variations, healing capacity, obesity, bone quality, and the capacity of the patient to tolerate major surgery. These factors, along with the mechanical goals of surgery, will help to predict both the impact and the risks of surgery and will allow the surgeon and patient to have a detailed discussion regarding the proposed operative intervention.

In 2012, Schwab et al. [20] published a study comparing spinopelvic parameters to clinical outcome. They defined an SVA of less than 50 mm as an anatomic success and an SVA of greater than 100 mm as an anatomic failure. Patients with an SVA in the intermediate range between 50 and 100 mm were excluded to allow a more definitive contrast between the study groups. Not surprisingly, patients that were deemed clinical failures were found to have significantly worse preoperative spinopelvic parameters. Interestingly, the amount of correction was similar in both groups, suggesting that patients with the more severe preoperative deformities received inadequate correction. Some patients were also identified with less severe spinopelvic deformities that were overcorrected, leading to suboptimal results [21]. This study highlights the necessity of patient-specific preoperative planning and the need to execute a deformity correction scheme capable of normalizing spinopelvic balance.

One vexing cause of treatment failure is reciprocal changes (RC). RC is a change in the alignment of the unfused portion of the spine after the completion of a deformity correction which leads to the recurrence of an unsatisfactory deformity. One study [22] looked at changes in thoracic kyphosis in conjunction with an osteotomy procedure of the lumbar region. The researchers found that 18 out of 34 total patients experienced unfavorable thoracic RC. A larger pelvic incidence, larger pelvic tilt, worse T1-spinopelvic inclination, and older age were found to be risk factors for RC following an osteotomy. Significant RC can lead to spinopelvic imbalance which can be as severe as the original deformity. Such a situation may necessitate revision surgery, often by extension of the fusion into the upper thoracic spine.

Implant failure constitutes another reason for osteotomy revision. Corrective spinal procedures place a substantial amount of mechanical stress on spinal implants. This situation may lead to screw pullout or rod/screw fracture, especially if healing of the fusion is delayed. In a study examining 442 patients treated with posterior instrumented fusion for adult spinal deformity, Smith et al. [13] found symptomatic rod fracture in 6.8 % of the patient cohort. The rate of rod fracture was higher in post-osteotomy population, where 15.8 % (18 out of 114) of patients treated with a pedicle subtraction osteotomy (PSO) experienced symptomatic rod fracture. Eighty-nine percent (16 out of 18) of the fractures occurred at or adjacent to the level of the PSO. Patients with persistent sagittal imbalance and obese patients were found to be at increased risk for rod fracture. When the data was analyzed for the composition of the broken rod, rod fracture was found in 7 % of cobalt chromium rods, 17 % of stainless steel rods, and 25 % of titanium rods.

Only gold members can continue reading. Log In or Register to continue