High-Grade Spondylolisthesis: Posterior Decompression and Spanning/Dowel Fibula

CHAPTER

Rick C. Sasso 66 James E. Lashley High-Grade Spondylolisthesis: Posterior Decompression and Spanning/Dowel Fibula

[Au1] BACKGROUND age slip as well as degree of symptoms.20 To this day, these treatment pathways have remained relatively unchanged. For First described by Herbiniaux in 1782, spondylolisthesis is low-grade (Meyerding 1 and 2) slips, treatment consists of activ- defi ned as the slippage of one vertebra upon another. With ity modifi cation, bracing, physical therapy, and a return to nor- regard to the pediatric population, the L5-S1 articulation is the mal activity once symptoms subside. Surgical intervention is most common site of slippage. In children and adolescents, the reserved for those patients in whom symptoms are not relieved cause of listhesis is dysplastic changes of the posterior elements by nonoperative means. In contrast, for patients presenting of L5 and superior articular facets of S1 and/or isthmic defects with high-grade slips (Meyerding 3, 4, and 5); surgical interven- of the posterior elements of L5 (usually the pars interarticu- tion is recommended regardless of the magnitude or duration laris). The overall incidence of spondylolysis in the American of symptoms. This is true for children due to the high potential population is approximately 6%, with a male to female ratio of for these high-grade slips to progress before skeletal maturity; 2:1. It has been found that a predisposition toward spondyloly- however, treatment recommendations for adults with a high- sis is higher in the Caucasian population than in the African- grade slip are less clear. American population and may be found in up to 50% of the Several surgical options currently exist for the treatment of 5–7 Eskimo populations of North America.4,18 high-grade isthmic spondylolisthesis. The one common ele- From an etiologic standpoint, spondylolisthesis is a multifacto- ment to all surgical interventions remains arthrodesis: in situ rial disease with heredity and environmental factors being most posterolateral fusion, posterolateral fusion and decompression, important.4 Recent studies conclusively demonstrate that isthmic posterolateral instrumented fusion, and posterolateral fusion spondylolisthesis is not present at birth. Although spondylolysis is combined with interbody fusion. Traditional techniques of pos- more commonly found in males, the propensity for slip progres- terolateral fusion, with or without decompression or instru- sion appears to be higher in females. The etiology for these gen- mentation, have been utilized in the treatment of high-grade 10 der differences is unknown. Spondylolysis is more common among slips, but only with moderate success. The unfavorable biome- those engaged in activities involving hyperextension of the lower chanical environment places the posterior graft bed under ten- spine such as gymnastics, football (linemen), wrestling, etc. sion; this, in turn, leads to increased potential for nonunion, Meyerding’s defi nition of degree of slippage, Wiltse’s etiologic postoperative progression of slip angle, and translation. Hanson classifi cation, and Marchetti’s and Bartolozzi’s descriptive classifi - et al have shown that the addition of an interbody fusion utiliz- cation to defi ne surgical parameters are the most commonly ing a spanning fi bula dowel not only leads to increased fusion 5 used classifi cation schemes to categorize spondylolisthesis.9,19–22 rates but also decreases postoperative slip progression. Along with these classifi cations, various other risk factors for slip Unfortunately, the abnormal morphology of the lumbosacral progression include slip angle of greater than 55°, female gen- junction prevents the use of traditional trapezoidal anterior der, early age of diagnosis, and degree of slip at presentation and posterior interbody grafts. To overcome this abnormal (Ͼ50% slip).20 From these radiographic parameters and classifi - offset of the L5 and S1 end plates, a technique utilizing trans- cation schemes, a useful algorithm to direct nonsurgical and vertebral interbody fi bular dowel grafts has met with great 5,17 surgical management of patients with spondylolisthesis has been success. developed. The advantage of this technique is the ability to achieve a circumferential construct to maximize the fusion rate without the necessity of a complete translational reduction of L5 on S1, TREATMENT which is required for traditional block-type interbody devices. The most compelling reason not to attempt a complete transla- More than 30 years ago, Wiltse and Jackson defi ned treatment tional reduction is the extremely high incidence of L5 nerve algorithms for pediatric spondylolisthesis based upon percent- root defi cit. Cadaveric studies demonstrate a relatively low 646

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planning is required. This includes planning for radiographic Surgical Technique for guidance of instruments and implants, neurophysiologic moni- High-Grade Isthmic toring, determination of anterior/posterior or posterior-only Spondylolisthesis with TABLE 66.1 approach as well as levels of instrumentation, and use of bone Associated Complications, graft extenders to enhance fusion. * Fusion Rate, and Complexity Placement of instrumentation is a technically demanding skill that requires intraoperative imaging to effect perfect place- L5 Nerve Fusion Surgical ment of guidewires and screws. Image-guided navigation and Technique Injury Rate Complexity real-time fl uoroscopy are two methods used to visualize place- Partial reduction with Rare High Low ment of instrumentation. At our institution, we utilize image- fi bular strut graft and guided navigation for placement of pedicle screws, as well as posterior pedicle choosing the direction of and determining the depth for guide- screws wire placement. After the right-sided buttock is sterilely Vertebrectomy (Gaines More High Highest prepped, a reference antenna is percutaneously placed into the procedure) common right posterior–superior iliac spine and preoperative scans are Complete reduction of More High High acquired in the operating room (Fig. 66.1). This provides the translational common ability to simultaneously visualize AP, lateral, and axial views in [Au2] component real time during the procedure and visualize our instrumentation in a virtual fashion on the computer screen (Fig. 66.2). * Posterior instrumented rare lower. Fusion in situ lowest. Pedicle screw length, reaming depth, and appropriate guidewire placement are all readily determined. In contrast to real- time fl uoroscopy, the surgeon, assistant, and operative fi eld are not crowded by two separate fl uoroscopic machines; radiation strain on the L5 nerve root with the fi rst 25% translational exposure to personnel is dramatically reduced; and less time is reduction of L5; however, this nerve root stretch increases 11 spent by avoiding the numerous single fl uoroscopic images exponentially with the fi nal 50% reduction. This technique with each step of instrumentation placement. allows for the achievement of a partial reduction of the slip. Neurophysiologic monitoring is an extremely useful tool to The most important aspect of this deformity correction is the help avoid catastrophic intraoperative nerve damage by surgi- sagittal angle. The lumbosacral kyphosis reduction is easily cal instruments (i.e., drills, taps, and probes) and instrumenta- achieved with positioning on the operating table, and partial tion (e.g., pedicle screws). Continuous electromyogram (EMG) [Au3] reduction of the translational deformity also frequently occurs monitoring helps prevent nerve root damage during pedicle with this procedure. It is important, however, not to attempt a screw placement, interbody cannulation, and fi bular allograft forceful reduction of the translation to limit the chance of neu- placement. During the posterior-only approach, preparation of ral defi cit (Table 66.1). the channel for the fi bular allograft requires retraction of the S1 nerve root laterally and the dura medially to provide enough space for passage of the reamers. Continuous EMG monitoring PREOPERATIVE PLANNING is also utilized during preparation and placement of pedicle screws. In addition, each pedicle screw is independently tested In order to increase the likelihood of successful fusion as well with direct electrical stimulation via a direct monopolar nerve as prevent intraoperative nerve damage, careful preoperative stimulator to assess pedicle wall integrity.

Figure 66.1. Intraoperative ﬂ uoronavigation scan outlining sagittal, coronal, and axial views of a slip.

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A B

Figure 66.2. Intraoperative ﬂ uoronavigation scan with projected trajectory of transsacral transvertebral ﬁ bular dowel graft through S1 into L5 body. (A) Intraop- erative picture with the navigation probe demonstrating the projected trajectory. (B) Coronal view of the intraoperative image navigation with the probe across the L5-S1 disc into the L5 vertebral body. (C) Sagittal view of the intraoperative image navigation showing the probe extending from the sacrum across the high-grade spon- C dylolisthesis docking into the L5 vertebral body.

Determination of the optimal surgical approach is a deci- tion. Classically, it has been taught that a high-grade spon- sion to be made between surgeon and patient. Benefi ts of a dylolisthesis is best treated with posterior instrumentation posterior-only approach are that it spares a separate anterior spanning L4 to S1. In the past, L5 pedicle fi xation was diffi cult incision, avoids complications of the anterior approach (e.g., to achieve due to the challenging local anatomy (translated retrograde ejaculation in a male), and limits the arthrodesis to and rotated L5 vertebra), and the tendency of the L4 and L5 only one level (L5-S1) if appropriate. On the other hand, a pedicle screws heads to abut. With our current technique, it is miniopen anterior lumbar interbody fusion approach can be now possible to include the L5 pedicle screw in an L4-S1 poste- utilized to gain access to the L4-L5 interspace, with placement rior construct. This is made possible through indirect reduc- of the fi bular dowel graft from L5 to S1 in an antegrade fash- tion of L5 on S1 by patient positioning (reducing the kyphosis ion. Advantages of the anterior approach are that it avoids the of L5 on S1), the use of modern polyaxial screw heads, and potential risks of S1 nerve root damage due to excessive retrac- image-guided navigation (Fig. 66.3). The addition of L5 pedi- tion and reamer contact with the nerve (Table 66.2). cle fi xation results in much stronger biomechanical construct The successful outcome of this circumferential fusion tech- and provides an excellent environment for fusion. Furthermore, nique is predicated upon the ability to achieve and maintain a if the L5 pedicle is considered to be strong enough and is eas- rigid construct composed of instrumentation and graft mate- ily accessible, it may be the most cephalad point of fi xation in rial. A stable biomechanical environment reduces micromo- the posterior fusion, thereby changing the treatment to a one- tion at the fusion interface and increases the likelihood of a level fusion (Fig. 66.4). successful arthrodesis. This is achieved with both fi bular To date, iliac crest autograft is still considered the gold stan- allograft, as well as posterior pedicle–screw/rod instrumenta- dard for achieving solid fusion of any posterior lumbar fusion.

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Circumferential Versus Posterior-Only Surgical Technique TABLE 66.2 for High-Grade Isthmic Spondylolisthesis with Associated Advantages and Disadvantages

Potential for Retrograde Ability to Place Strong Ejaculation in Young and Large Interbody Potential for S1 Technique Incisions Male Construct in L4-5 Disc Nerve Irritation

Posterior-only 1 No No Yes Anterior and 2 Yes Yes No posterior

Over the last decade, innovations in bone graft extenders and the ulnar nerves with elbows fl exed and glenohumeral joints recombinant bone morphogenic protein (BMP) have enabled us forward fl exed 90°. Likewise, the common peroneal nerves are to enhance fusion mass while potentially avoiding the morbidity “padded” with egg crate mattresses. of iliac crest bone graft harvesting. We use a combination of After placement of the percutaneous image-guided naviga- biphasic calcium phosphate with BMP-2 as the graft material for tion reference antenna into the posterior superior iliac spine the posterior fusion mass. The local autograft bone from the Gill (PSIS), a scan is acquired (Fig. 66.1). A preoperative antibiotic laminectomy is also cut into small pieces and mixed into the graft. is administered, and the patient is then prepped and draped in It must be understood that this is considered an off-label use of a sterile fashion to allow an operative fi eld from L1 to the supe- these products in the treatment of high-grade spondylolisthesis. rior gluteal crease. A standard midline exposure is made from the L3-L4 facet joints to the sacrum. Great care is taken during exposure over the sacrum due to the well-established associa- TECHNIQUE tion of spondylolisthesis and spina bifi da occulta. Once exposed, a standard Gill laminectomy of L5 is performed. POSTERIOR APPROACH Fibrous tissue from the nonhealed pars defects are debrided (in cases with associated spondylolysis) and both L5 nerves are The patient is placed under general endotracheal anesthesia completely decompressed. Standard posterior pedicle screw on the hospital bed. Once asleep, a Foley catheter is placed, instrumentation is then placed from the L4 to S1 pedicles. EMG leads are placed upon the lower extremities, and thigh- Laminectomy of S1 is performed to expose the S1-S2 interspace high compression stockings and sequential compression devices and overlying dural sac, the S2 pedicles, as well as the S1 and S2 upon the calves. The patient is then placed into a prone posi- nerve roots. Next, the dural sac is retracted medially, between tion on the Jackson table with care taken to place pads across the S1 nerve root and S2 pedicle, to reveal the entry site into the chest (above nipples) and at the anterior-superior iliac the body of the sacrum. The entry site is centered 1 cm lateral spines, while the legs are suspended in the leg “sling.” This to the midline of the S1 body at the level of the hypoplastic position allows the abdomen to be freely suspended and S1-S2 disc. The planned depth of the channel to be reamed is achieves an indirect reduction of the slip by extension of the approximately 80% of the posterior–anterior length from the hips. Arms are placed upon egg crate mattresses cushioning entry site at the S1 body to the anterior cortex of L5. This

Figure 66.3. An anterior–posterior circumferential fusion, which includes the L5 pedicle screws in the posterior instrumented Figure 66.4. A posterior-only approach construct with L5 pedicle construct. screws allowing a one-level fusion.

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length avoids inadvertent penetration of the anterior aspect of hemostasis is obtained. The wound is then closed in layers. the L5 body. The patient is placed into supine fashion onto the hospital With use of fl uoroscopic control or computer navigation, bed and awakened from general anesthesia. a standard 2-mm guidewire is advanced from the entry site through the S1 body across the L5-S1 interspace into the ANTERIOR–POSTERIOR APPROACH anterior cortex of the L5 body (taking care not to penetrate the anterior L5 cortex). At our institution, we utilize image The patient is placed under general endotracheal anesthesia navigation for placement of pedicle screws and for determin- on the hospital bed. Once asleep, a Foley catheter is placed; ing the path of guidewire placement from S1 into L5. In addi- EMG leads are placed upon the lower extremities as are thigh- tion, image navigation is used to determine the appropriate high compression stockings and sequential compression length of the fi bular allograft. Next, a fi bular allograft, devices upon the calves. The patient is then transferred supine roughly cylindrical in shape, is cut to the appropriate length to a radiolucent table. A percutaneous image-guided naviga- with a saw. This length is 1 to 2 mm shorter than the depth of tion antenna is placed into the anterior-superior iliac spine the reamed channel. This allows the graft to be recessed under sterile technique, and a preoperative scan is acquired. below the level of the reamed channel at the entry point in A preoperative antibiotic is administered, and the patient is the posterior sacral wall. The cut allograft is shaped with a then prepped and draped in sterile fashion. In the supine burr to remove the sharp edges at either end and along the position, the hips are allowed to be in an extended position axis to fashion the graft into a cylindrical shape. The fash- (do not place pillows under the thighs) to obtain positional [Au4] ioned graft is then measured with the ACL sizer to obtain the correction of the sagittal deformity at L5-S1. A standard, left- most accurate diameter (see Fig. 66.14). The leading edge of sided, paramedian, rectus-sparing, miniopen, retroperitoneal the graft is carefully tapered to allow easy entry into the approach is performed to expose the L4-L5 interspace reamed channel. Standard ACL reamers are passed over the through a transverse skin incision. This is a routine approach guidewire in sequential fashion to ream a channel 1 mm less to the L4-5 disc, and the L5-S1 disc is not even visualized. This than the cross-sectional diameter of the fi bular strut allograft is important because the high-grade slip makes the anatomy (Fig. 66.5). The guidewire is removed, and the fi bular strut at L5-S1 very abnormal and impossible to expose through a dowel is then driven into the reamed channel. The dowel is retroperitoneal approach. Exposing the L5-S1 disc in a high- gently tapped into the channel with use of a small tamp and grade slip requires a transperitoneal approach, which is elim- mallet until the posterior aspect of the dowel is recessed 1 to inated in the present technique by accessing the L5-S1 disc 2 mm below the entry point of the reamed channel; this will through the L4-5 disc space. The L4-L5 disc is carefully prevent impingement of the anterior aspect of dura and excised, and the cartilaginous end plates of L4 and L5 are nerve roots upon a protruding graft. The process is repeated removed down to the strong subchondral bone. A 2-mm on the contralateral aspect of the sacrum to place a second guidewire is placed in the midportion of the cephalad L5 end S1-L5 interbody dowel graft, and the dura is then retracted plate. The guidewire is then drilled through the cephalad L5 over the fi rst reamed channel and graft. Two rods are then end plate, into the L5 body, across the L5-S1 interspace, into placed into their corresponding pedicle–screw heads on each the S1 body and docking at the hypoplastic S1-S2 interspace. L4-S1 (or L5-S1) construct, set screws are placed, and fi nal Sequential reaming is then performed to prepare a channel 1 tightening of set screws is performed to hold the position of mm less than the cross-sectional diameter of the fi bular dowel L5-S1. Decortication of transverse processes (at L4 and L5) graft. The guidewire is removed, and the dowel graft is placed and sacral alae is carried out; BMP-2 sponges, bone graft into the channel. The graft is then carefully advanced, with a extender, and local autogenous bone graft (from laminec- tamp and mallet, until the proximal end of the graft is recessed tomy) are placed in the lateral gutters; and appropriate approximately 1 mm less than the entry point of the cephalad L5 end plate. A trapezoidal femoral ring allograft packed with a BMP-soaked sponge is then placed in the L4-L5 interspace. As in the posterior procedure autograft reamings from the drill are saved and mixed with the bone graft. Appropriate hemostasis is obtained, all vascular structures are checked, and the wound is closed in layers. Next, the patient is placed in the prone position on a Jackson frame (as described in the posterior approach, above). A standard midline exposure is made from the L3-L4 facet joints to the sacrum. Great care is taken during exposure over the sacrum due to the well-established association of spondylolisthesis and spina bifi da occulta. Once exposed, a standard Gill laminectomy of L5 is performed. Fibrous tissue from the nonhealed pars defects are debrided, and both L5 nerves are completely released. Standard posterior pedicle screw instrumentation is then placed from the L4 to S1 pedicles, including the L5 pedicles if possible. Rods are inserted and set screws placed and tightened, as described above. Decortication is carried out; bone graft and graft extenders (if used) are placed in the pre- Figure 66.5. Reaming of the channel for placement of the fi bular pared lateral gutters. Hemostasis is obtained, and the wound is dowel graft. closed in layers (Figs. 66.6 and 66.7).

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day 1, the Foley catheter is discontinued, the wound is checked, and pain control is slowly transitioned to oral analgesics. The patient is progressively ambulated with assistance by physical therapy and then discharged to home once ambulating satisfac- torily, usually 3 to 4 days after surgery.

RESULTS Circumferential fusion with posterolateral graft and interbody fi bular strut grafting has a long history of success.1,3,5,10,15,16 Bohlman and Cook fi rst described the posterior-only approach in two patients in 1982.1 Short-term follow-up of both patients showed resolution of preoperative pain and neurologic defi cits with solid arthrodesis at 2 years. A subsequent study by Smith and Bohlman evaluated 11 skeletally mature patients with high-grade slips who underwent a sin- Figure 66.6. Lateral radiograph of an anterior–posterior gle-stage posterior approach interbody arthrodesis with pos- approach circumferential fusion with L4-S1 screws, posteriorly, and terolateral fusion for up to 12 years.16 Once again, a solid L4-L5 interbody graft overlying the entry point for the fi bular dowel arthrodesis was obtained with improvement of preoperative graft (outlined in black). neurologic defi cits in all patients. Esses et al assessed the outcomes of nine patients who underwent a single-stage posterior approach circumferential arthrodesis with fi bular strut POSTOPERATIVE CARE grafts.3 In addition to showing solid fusion at 1 year, all nine patients had signifi cant reductions in their back pain Visual The patient is advanced to standing at bedside with physical Analog Scale (VAS) scores. Molinari et al conducted a retro- therapy on the same day of surgery. If the patient underwent an spective comparison of three different treatments of high- [Au5] anterior–posterior approach, they are kept NPO until passing grade spondylolisthesis slips: (1) posterolateral in situ fusion fl atus, and then diet is advanced slowly. Otherwise, if posterior- without decompression, (2) posterolateral fusion with instru- only approach is utilized, diet is started right away. Patient-con- mentation and decompression, and (3) decompression, trolled analgesia is utilized for pain control. By postoperative reduction, and circumferential fusion (both anterior–posterior approach and posterior-only approach).10 The pseudarthrosis rates for the three groups were 45%, 29%, and 0%, respectively. Although no signifi cant differences regarding pain, function, and satisfaction were found among the three groups, the third group scored highest in all parameters. Sasso et al reported the results of 25 patients undergoing posterior decompression and circumferential fusion with both techniques (anterior–posterior and posterior-only). All 25 patients achieved solid arthrodesis, with no progression of slip, and 96% extremely satisfi ed/satisfi ed on SRS functional outcome scoring.13 [Au6] When it comes to allograft versus autograft, Hanson et al showed no difference in rates of remodeling between the two grafts. Therefore, they recommended that allograft is an accept- able treatment option for strut grafting (Table 66.3).5

COMPLICATIONS In the treatment of high-grade spondylolisthesis, numerous complications have been outlined in the literature. In regard to in situ posterolateral fusion, high rates of pseudarthrosis, progression of slip despite solid fusion, cauda equina syndrome, and neurologic complications are most notable.8,14 Posterior fusion supplemented with posterior instrumentation alone has been further complicated by failure of instrumentation, subsequent pseudarthrosis, and progression of slip.2,10 It has been postulated that the biomechanical stability afforded by an interbody graft may reduce not only the rate of Figure 66.7. Anteroposterior radiograph depicting the same ante- pseudarthrosis, but also reduce the chance of postfusion slip rior–posterior approach circumferential fusion. progression. High success rates are reported throughout the

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Details of the Literature on the Surgical Outcome of TABLE 66.3 High-Grade Isthmic Spondylolisthesis

Study Author Patients Fusion Rate Reduction Complications Clinical Success

Sasso 25 100% No loss of Translation No neurologic 96% Extremely correction improved 0.2 defi cits satisfi ed/ grades. Slip satisfi ed angle improved 10° Hanson 17 100% No loss of Translation No neurologic Excellent correction improved 1.4 defi cits grades Slip angle improved 14° Smith 9 100% No neurologic Excellent defi cits Esses 9 100% Excellent based No permanent on VAS scores defi cits One dural tear Two infections at fi bular autograft harvest site

VAS, Visual Analog Scale.

literature when high-grade slips are treated with circumferen- tomically translating L5 upon S1. Certain measures may be tial fusion.1–3,5,10,14–16 As evidenced by the comparative study of taken to diminish the chance of postoperative L5 dysfunc- Molinari et al, circumferential fusion was associated with the tion. These include intraoperative continuous EMG monitor- lowest rate of pseudarthrosis (0%).10 This relevant and impor- ing, and indirect partial reduction of spondylolisthesis by tant comparative study clearly supports the performance of a patient positioning with the hips in extension, prior to inci- circumferential fusion for this diffi cult condition of a high- sion. Although many cases of postoperative L5 dysfunction grade isthmic spondylolisthesis. Without an interbody con- are reported to resolve, some are permanent. It is the author’s struct, a high rate of complications and pseudarthrosis can be opinion that reduction of L5 on S1 is best gained through expected. As with any spinal fusion procedure, there is always positional “indirect” partial reduction as opposed to vigorous the potential for failure of instrumentation and loss of fi xa- attempts to obtain an anatomic reduction of L5-S1 translation/reduction. Variable rates of loss of fi xation have been tion prior to fi xation and fusion. In this instance, partial observed even in circumferential fusion procedures, but at a reduction of L5 on S1 to correct the sagittal imbalance is lower rate than that seen in posterolateral fusion with pedicu- more important than obtaining a full translational reduction lar fi xation alone.2,10 of L5 on S1. To date, there is no literature supporting The most concerning complication remains postoperative improved outcomes with full reduction of the translation of neurologic defi cit. Most cases of defi cit involve the L5 nerve L5 onto S1. The most important goal to achieve a good out- root manifesting as postoperative foot drop and are believed come is to achieve a solid fusion. This is appropriately accom- to be due to overzealous reduction of the L5-S1 level. Petraco plished with a solid circumferential fusion utilizing a fi bular et al performed a cadaveric study to examine L5 nerve strain dowel strut graft and posterolateral fusion mass with pedicle with reduction maneuvers of slipped L5-S1 constructs.11 They screw instrumentation. found that the initial 50% of anatomic reduction of L5 upon Other complications reported are those associated with spi- S1 was associated with only 21% of nerve strain, and that the nal fusion procedures in general. These include durotomy, second half of reduction was associated with 79% strain of infection, deep venous thrombosis, and retrograde ejaculation the L5 nerve. In addition, they found that less strain occurred associated with anterior approaches to the lumbosacral when only slip angle was reduced when compared with ana- spine.7,12

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[Au7] CASE 66.1

JB is a 13-year-old competitive high school tennis player intraoperative image-guided scan was acquired (Fig. with low back pain. Eight months prior to presentation, 66.1). The patient was then prepped and draped in ster- the patient had a short episode of low back pain follow- ile fashion. A standard midline incision was made, and ing a basketball game, which resolved spontaneously. great care taken during deeper dissection because of Approximately 3 weeks prior to presentation, JB experi- suspected spina bifi da occulta as visualized on preopera- enced an exacerbation of low back pain with worsening tive radiographs. The L5 and S1 vertebrae were identi- gait disturbance following a tennis match. At the time of fi ed, and dissection was carried out laterally to visualize presentation, the patient described the presence of dyses- the transverse process of L5 as well as sacral ala at S1. In thesias in the left leg and foot. The history was otherwise this case, it was possible to place pedicle screws at L5 unremarkable. and S1 under image-guided navigation. Based upon the Physical examination is notable for hamstring tight- large transverse processes of L5 (as a bone grafting sur- ness, a vertical pelvis, an abdominal crease, hyperlordosis face), good sagittal alignment of L5 on S1, and excel- above the lumbosacral junction, and a gait disturbance lent pedicle fi xation into L5, it was decided that L5 consisting of fl exed hips and knees with ambulation would be the highest level included in the posterior (Figs. 66.8 and 66.9). Examination revealed the lower fusion construct. A Gill laminectomy of L5 with subse- extremity myotomes and dermatomes to be intact without quent decompression of the L5 nerves was performed, loss of strength. Radiographic examination displays a and then a laminectomy of S1 to visualize the S1 and S2 high-grade slip (Meyerding 4) at the lumbosacral junc- nerve roots and S2 pedicle. Sequential reaming of the tion, with dysplastic changes of the sacral dome and trap- channel for the left fi bular strut graft was performed to ezoidal L5 body (Figs. 66.10 and 66.11). an ACL reamer diameter of 10 mm, and depth of chan- With continued pain, having previously failed non- nel measured (Fig. 66.13). For this patient, the length operative management, and most notably the high of the strut was 30 mm, and the diameter was 11 mm degree of slip in this young individual, operative inter- (Fig. 66.14). The fi bular strut graft was then carefully vention was discussed. Surgical options were discussed fashioned such that the length of the graft was 2 mm including interbody fusion with fi bular strut grafts shorter than the depth of reamed channel. This process (anterior vs. posterior approach) with posterolateral was repeated for placement of the right fi bular strut fusion and instrumentation. Attendant complications graft. Decortication in the lateral gutters was performed, and expected outcomes were also discussed. Because of and Infuse®, Mastergraft®, and local autograft were the potential for retrograde ejaculation with an ante- placed in the lateral gutters. The patient was awakened rior approach and desire to spare the normal L4-5 from general anesthesia and then transferred to PACU [Au8] motion segment (Fig. 66.12) the patient/family decided and then to the fl oor. The postoperative course was upon posterior-only approach. This approach also uneventful with the exception of 4/5 strength of left allowed the potential for a limited L5-S1 arthrodesis ankle dorsifl exors. Immediately after surgery, the since the L4-5 disc was normal on magnetic resonance patient’s gait was markedly improved. Two months post- imaging (MRI). operatively, the ankle dorsifl exion weakness had A posterior-only approach was used to obtain fi xation resolved and the patient was pain-free. Radiographs dis- and fusion of this high-grade slip. The patient was play early fusion and JB is currently engaged in nonim- placed prone on a Jackson table, providing partial indi- pact aerobic activities without diffi culty. (Figs. 66.15 and rect reduction of the slip through maximal hip extension. 66.16) At 4 months after surgery, patient is back to play- A percutaneous reference antenna, for image-guided ing competitive tennis. navigation, was placed under sterile technique. An

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Figure 66.10. Upright lateral radiograph depicting characteristics of high-grade spondylolisthesis including trapezoidal L5 body and rounded sacral dome, junctional kyphosis at lumbosacral junction, and a Meyerding grade 4 translation.

Figure 66.8. Typical posture of high-grade spondylolisthesis depicting kyphosis of lumbosacral junction, vertical position of the sacrum, and ﬂ exion of hips and knees in upright standing.

Figure 66.9. Scaphoid abdomen of a high-grade spondylolisthesis patient with characteristic abdominal crease. Figure 66.11. Close-up lateral radiograph of grade 4 slip.

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Figure 66.14. Prepared ﬁ bular graft measuring 30 mm (2 mm less than reamed depth of prepared channel) adjacent to ACL graft [Au16] measuring tool.

Figure 66.12. Magnetic resonance imaging of grade 4 slip. Note hydration and height of L4-L5 disc space.

Figure 66.15. Lateral radiograph for ﬁ nal reduction and circumferential fusion of grade 4 slip.

Figure 66.13. Sequential reaming over guidewire preparing channel for ﬁ bular dowel graft.

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Figure 66.16. Anteroposterior radiograph of ﬁ nal reduction and circumferential fusion of grade 4 slip.

CASE 66.2

JG is a 14-year-old competitive soccer player referred During placement of pedicle screws, it was felt that the L5 from an outside team physician for a chief complaint of pedicles were neither accessible nor strong enough to provide hamstring tightness. Evaluation revealed a high-grade suffi cient pedicle screw fi xation. Therefore, the pedicle screw L5-S1 spondylolisthesis. The patient presented with the instrumentation and subsequent graft material spanned the insidious onset of hamstring tightness. The patient did distance of L4 to S1. A Gill laminectomy of L5 was performed, not remember any inciting event or history of back pain. and both L5 nerve roots were decompressed. Laminectomy of Physical examination is notable for hamstring tightness, S1 was carried out, and careful retraction of the left S1 nerve an abdominal crease, and hyperlordosis above the lum- root laterally and the dura medially was performed to visual- bosacral junction (Fig. 66.17). Neurologic examination of ize the entry point for the guidewire. Sequential reaming was the lower extremities reveals intact myotomes and der- carried out; a fi bular dowel graft was fashioned and then matomes with 5/5 muscle strength. Radiographic examina- advanced through the prepared channel. This process was tion revealed a grade 4 slip (Figs. 66.18 and 66.19). then repeated on the contralateral side. Once the fi bular Surgical options including circumferential fusion with fi b- grafts were placed, decortication of the transverse processes ular dowel graft and posterolateral graft with instrumentation and sacral alae was performed. Care was taken to decorticate were discussed. After careful consideration, the patient chose the transverse processes of the L5 body so that they would be to undergo surgical treatment via a posterior approach. included in the posterolateral fusion mass. Local autograft, The operation consisted of a posterior-only approach as biphasic calcium phosphate, and BMP-2 were placed in the described above. The patient was placed into a prone posi- lateral gutters. Hemostasis was obtained and the wound closed tion upon the Jackson table, a percutaneous image-guided in layers. Postoperative radiographs were obtained (Figs. 66.20 antenna placed into the PSIS with sterile technique, intra- and 66.21). After surgery, hamstring tightness resolved. At 2 operative scan acquired, and then prepped and draped in years after surgery, the graft has healed and the patient is now sterile fashion. The standard midline incision was made, competing in soccer at a national level (Figs. 66.22 deep dissection carried out to visualize the L4 to S1. to 66.24).

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Figure 66.19. Anteroposterior radiograph depicting the “Napo- leon Hat” sign of this grade 4 slip.

Figure 66.17. Posture of high-grade slip depicting junctional kyphosis of lumbosacral junction, vertical positioning of pelvis, and hamstring tightness with ﬂ exed knees and ﬂ exed hips.

Figure 66.20. Final lateral radiograph of this posterior-only approach circumferential fusion including instrumentation from L4-S1 and ﬁ bular dowel graft.

Figure 66.18. Lateral radiograph depicting grade 4 slip characteristics including a trapezoidal L5 body, domed sacrum, and kyphosis of the lumbosacral junction.

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Figure 66.21. Final anteroposterior radiograph of this posterior- only approach circumferential fusion.

Figure 66.23. Clinical picture at 2 years postoperatively; note improvement in posture as compared with preoperative picture (Fig. 66.19). [Au17]

Figure 66.24. JG participating in world-class competitive soccer match 2 years after surgery.

Figure 66.22. Lateral radiograph of circumferential fusion at 2 years postoperatively; note incorporation of ﬁ bular dowel graft in interbody fusion mass (compared to Fig. 66.23).

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4. Fredrickson BE, Baker D. The natural history of spondylolysis and spondylolisthesis. J Bone CONCLUSIONS Joint Surg Am 1984;66:699–707. [Au9] 5. Hanson DS, Bridwell KH, Rhee JM, Lenke LG. Dowel fi bular strut grafts for high-grade This technique of driving a fi bular strut allograft across the dysplastic isthmic spondylolisthesis. Spine 2002;27(18):1982–1988. [Au10] 6. Laurent LE, Osterman K. Operative treatment of spondylolisthesis in young patients. Clin disc of a high-grade spondylolisthesis at the lumbosacral Orthop Relat Res 1976;117:85–91. junction to afford an interbody fusion in combination with 7. Lehmer SM, Steffee AD, Gaines RW Jr. Treatment of L5-S1 spondyloptosis by staged L5 posterior instrumentation is a very successful strategy. Partial resection with reduction and fusion of L4 onto S1 (Gaines procedure). Spine 1994;19(17):1916–1925. reduction is obtained with specifi c attention to the sagittal 8. Lonner BS, Song EW, Scharf CL, Yao J. Reduction of high-grade isthmic and dysplastic slip angle. This is the preferred method for the surgical spondylolisthesis in 5 adolescents. Am J Orthop 2007;36(7):367–373. [Au11] treatment of high-grade isthmic spondylolisthesis because of 9. Marchetti PG, Bartolozzi P. Classifi cation of spondylolisthesis as a guideline for treatment. In The textbook of spinal surgery, 2nd ed. Philadelphia, PA: Lippincott-Raven, 1997:1211–[Au12] the very high fusion rate, low L5 nerve root defi cit rate, low 1253. incidence of complications, and high patient satisfaction. 10. Molinari RW, Bridwell KH, Lenke LG, Ungacta FF, Riew KD. Complications in the surgical treatment of pediatric high-grade, isthmic dysplastic spondylolisthesis: a comparison of This is also a reasonable technique to use in a salvage situa- three surgical approaches. Spine 1999;24(16):1701–1711. tion where the patient has already undergone surgical treat- 11. Petraco DM, Spivak JM, Cappadona JG, Kummer FJ, Neuwirth MG. An anatomic evalua- ment for a high-grade spondylolisthesis but failed due to tion of L5 nerve stretch in spondylolisthesis reduction. Spine 1996;21(10):1133–1138. 12. Sasso RC, Burkus JK, Le Huec JC. Retrograde ejaculation after anterior lumbar interbody nonunion and deformity progression. This strategy is useful fusion. Spine 2003;28(10):1023–1026. in adults as well as the pediatric population. This procedure, 13. Sasso RC, Shively KD, Reilly TM. Trans-vertebral Trans-sacral strut grafting for high-grade isthmic spondylolisthesis L5-S1 with fi bular allograft. J Spinal Disord Tech 2008;21:328–333. [Au13] however, requires a Meyerding grade 3 or higher spondylolis- 14. Schoenecker PL, Cole HO, Herring JA, Capelli AM, Bradford DS. Cauda equina syndrome thesis. If the slip is a grade 2 or less then the trajectory of the after in situ arthrodesis for severe spondylolisthesis at the lumbosacral junction. J Bone fi bular strut is very diffi cult to achieve. The path of the strut Joint Surg Am 1990;72:369–377. 15. Smith JA, Deviren V, Berven S, Kleinstueck F, Bradford DS. Clinical outcome of trans-sacral graft in a high-grade situation is perpendicular to the inci- interbody fusion after partial reduction for high-grade L5-S1 spondylolisthesis. Spine sion, as the slip becomes less than grade 3; the course of the 2001;26(20):2227–2234. reamer becomes more parallel to the longitudinal axis of the 16. Smith MD, Bohlman HH. Spondylolisthesis treated by a single-stage operation combining decompression with in situ posterolateral fusion and anterior fusion. An analysis of eleven patient. Grade 2 and less deformity, however, allows applica- patients who had long-term follow-up. J Bone Joint Surg Am 1990;72:415–421. tion of more traditional trapezoidal interbody grafts. 17. Smith MD, Bohlman HH. Posterior decompression, sacrectomy, and anterior fi bular lumbosacral and posterolateral fusion for high grade spondylolisthesis. In The textbook for spinal surgery, 2nd ed. Philadelphia, PA: Lippincott Raven, 1997:1349–1356. [Au14] 18. Stewart TD. The age incidence of neural-arch defects in Alaskan Natives, considered from REFERENCES the standpoint of etiology. J Bone Joint Surg Am 1953;35:937–950. 19. Wiltse LL. The etiology of spondylolisthesis. J Bone Joint Surg Am 1962;44:539–560. 1. Bohlman HH, Cook SS. One-stage decompression and posterolateral and interbody 20. Wiltse LL, Jackson DW. Treatment of spondylolisthesis and spondylolysis in children. Clin fusion for lumbosacral spondyloptosis through a posterior approach: report of two Orthop Realt Res 1976;117:92–100. cases. J Bone Joint Surg Am 1982;64:415–418. 21. Wiltse LL, Newman PH, MacNab I. Classifi cation of spondylolysis and spondylolisthesis. 2. Boos N, Marchesi D, Zuber K. Treatment of severe spondylolisthesis by reduction and Clin Orthop Relat Res 1976;117:23–29. [Au15] pedicular fi xation. Spine 1993;18(12):1655–1661. 22. Wiltse LL, Winter RB. Terminology and measurement of spondylolisthesis. J Bone Joint 3. Esses SI, Natout N, Kip P. Posterior interbody arthrodesis with a fi bular strut graft in Surg Am 1983;65:768–772. spondylolisthesis. J Bone Joint Surg Am 1995;77:172–176.

LLWBK836_Ch66_p646-659.inddWBK836_Ch66_p646-659.indd 659659 55/19/11/19/11 112:08:062:08:06 PPMM AU1: Please check whether the heading levels are OK as typeset. AU2: Please spell out AP, if deemed necessary. AU3: Please check the expanded form of EMG. AU4: Please provide full form of ACL, if deemed necessary. AU5: Please spell out NPO, if deemed necessary. AU6: Please defi ne “SRS,” if deemed necessary. AU7: Please provide the Case captions for Cases “66.1 and 66.2.” AU8: Please spell out PACU, if deemed necessary. AU9: Please note that reference 3 has been updated from the Web site pdfs.journals.lww.com. AU10: Please note that author names in references 5, 8, 10, 11, 13, 14, and 15 have been updated from PubMed. AU11: Please note that author names in reference 7 have been updated from the Web site web.jbjs.org.uk. AU12: Please provide the names of editors in reference 9. AU13: Please note that author names in reference 12 have been updated from the Web site journals.lww.com. AU14: Please provide the names of editors in reference 17. AU15: Please note that author names in reference 20 have been updated from the Web site www.jaaos.org. AU16: Please spell out ACL in the fi gure legend of “Figure 66.14.” AU17: Note that in the fi gure legend of “Figure 66.23” there is a cross-reference to “Figure 66.19” where it is mentioned as a picture, whereas Figure 66.19 is an X-ray image. Please check.

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