High grade spondylolisthesis includes severe slips more than 50% and includes Meyerding's Grades III to V. Most often they are isthmic in nature and involve L5-S1. The patients can present during adolescence or in early adult life. Not uncommonly they may present middle aged as well. The main complaints include chronic back ache with leg pain. The leg pain may be referred or radiating pain. The radiculopathy is usually because of the compressed L5 nerve root. Also, there is associated sagittal plane deformity with a typical posture especially pronounced in cases of spondyloptosis (Meyerding Grade V spondylolisthesis).

Symptomatic high grade spondylolisthesis are managed surgically. There are different surgical methods and techniques described in the literature to treat high grade listhesis. They include decompression alone (Gill procedure), decompression with complete reduction and fusion, decompression with partial reduction and fusion, decompression with insitu fusion, and L5 vertebrectomy and reduction of L4 to S1 and fusion (Gaines procedure). There are different techniques in achieving insitu fusion which may be anterior, or posterior, or both anterior and posterior, or transacral fusion. Each one is described below.

Posterior decompression without fusion
In 1955, Gill et al described this decompression procedure for symptomatic isthmic spondylolisthesis (Gill et al, 1955). The free lamina of L5 (because of pars defect bilaterally) was found to be mobile in most instances, however sometimes its mobility might be restricted when the interspinous ligament between the L4 and L5 was tight. Also, in some patients there was excessive mobility of the loose lamina of L5 pressing on the fibrocartilagenous mass at the pars defect resulting in compression of L5 nerve root. Further, the rocking of L5 lamina resulted in traction of the S1 nerve roots where they pass toward the first sacral foramen. Gill described this procedure by starting to remove the spinous processes of L4, L5 and S1. Then the loose L5 lamina is removed. The ligamentum flavum is then excised starting from L4 down completely for better exposure. The lateral portion of the loose arch of L5 was then removed and the inferior articular process freed from its articulation from the sacrum. The L5 nerve root was then exposed and then retracted towards the midline away from the lateral wall and the fibrocartilagenous mass at the pars defect. This mass should be removed to decompress the nerve root completely. The root should be dissected free until the intervertebral foramen. Sometimes additional bone must be removed from the pedicle to decompress the L5 nerve root completely. Gill et al showed that by performing this procedure, the patients not only had relief of radiculopathy but also relief of back pain as well. Currently, Gill procedure by itself has gone into disfavour because of instability and progression of slip following such an extensive decompression (Lee, 1983). Recently, in 2006, Arts et al showed that a disease-free survival rate of 79% at 5 years and 72% at 10 years after the Gill's procedure using Kaplan-Meier's survival analysis (Arts et al, 2006).

Decompression with Complete reduction of listhesis and fusion
Complete reduction of listhesis results in correction of sagittal imbalance thereby improving the clinically apparent deformity associated with high grade slips. Further, this also reduces the tension on the fusion mass. Also, it improves the gait by reducing the deformity associated with it.

O'Brien, Mehdian and Jaffray described a procedure that involved posterior decompression of the spine along wth L5 and S1 nerve roots followed by gradual skeletal traction with serial radiographs at regular intervals to assess reduction of the listhesis (O'Brien et al, 1994). When adequate reduction was achieved then anterior interbody fusion was performed using an iliac crest bicortical bone graft. In patients where adequate reduction was not achieved, to secure the bone grafts, a supplementary AO lag screw was used. This was then followed by a plaster cast from nipple line to the knees and continued until satisfactory fusion. The cast was changed at 3 months. The authors reported good reduction in 20/22 cases. They had only two cases of permanent neurological damage in 22 patients consisting of foot drop.

Sijbrandij described a one-stage technique of reduction and stabilisation of severe grade slips via posterior approach. He obtained reduction using Harrington rods to lift L5 vertebral body out of pelvis and two double-threaded screws to pull it backwards (Sijbrandij, 1983). Stabilisation was then achieved by means of screws and a sacral bar. The Harrington rods were removed once reduction was achieved. Also, to acoid tension on the nerve roots, bone was resected from the L5 and S1 vertebral bodies. He reported no further slip in the three patients in his series.

Ruf et al recently described complete reduction of the high grade slip and monosegmental fusion in 27 patients (Ruf et al, 2006). They described an extensive decompression similar to Gill's followed by distraction between L4 and sacrum resulting in partialreduction of L5 vertebral body facilitating L5 pedicle screw entry. The L5/S1 disc was then cleared and the posterior longitudinal ligament was removed to prevent compression after complete reduction. The pedicle screw instrumentation was then used to achieve complete reduction of L5 on S1 by pulling the vertebral body against the rod. Even though this reduced the L5 on S1 there would still be lumbosacral kyphosis because of distraction.The L5/S1 disc space is filled with bone graft anteriorly and titanium cage posteriorly. Now, the posterior aspect is compressed by the instrumentation to achieve lumbosacral lordosis. According to the authors this posterior instrumentation combined with compression loaded cages anteriorly resulted in a very stable, shear resistant construct. 23/27 patients were free of pain at aminimum follow-up of 2 years.

Decompression with partial reduction and fusion
Partial reduction and fusion after decompression has the advantage of less complications compared to complete reduction, however with the preservation of deformity correction and its benefits. Smith et al described a procedure where they performed Gill's type posterior decompression followed by partial reduction and stabilisation with transacral fibular graft and posterolateral fusion with pedicle screw instrumentation (Smith et al, 2001). They reported this procedure in nine patients on whom the average preoperative slip angle of 41.20 was improved to an average postoperative slip angle of 210. All the patients had satisfactory outcome in their series. The fibular graft fractured in two patients where supplementary pedicle screw fixation was not used. When this was added subsequently fusion was achieved.

Decompression with insitu fusion
As reduction of the high grade spondylolisthesis was associated with significant temporary and permanent neurological deficit, insitu fusion was performed commonly most surgeons with good results. After a routine posterior decompression, fusion was achieved via a posterior, anterior or combined approach. Different techniques were used with or without instrumentation. Further, interbody fusion was achieved from posterior approach by transacral fixation either using strut grafts or instrumentation.

Bohlman and Cook described the transsacral fixation using fibular strut grafts in 1982 (Bohlam & Cook, 1982). The fibular strut graft was passed from the posterior aspect of S1 vertebral body (after removing the posterior elements while performing decompression), towards the disc space of L5/S1 crossing it and passing through the slipped L5 vertebral body. This was evaluated by the authors in eleven patients in 1990, with good results and no pseudoarthrosis. Roca et al added sacroplasty to this procedure by resecting the posterior aspect of sacrum to avoid future cauda equine compression (Roca et al, 1999).

Abdu et al described pedicular transvertebral screw fixation of lumbosacral spine in high grade slips whereby the S1 pedicle screw was passed in such a way to cross the L5/S1 disc space and hold the L5 vertebral body in place without any reduction of the slip (Abdu et al, 1994). The fusion was performed from L4 to S1 with the L5 vertebral body held by the S1 pedicle screws. This gave good results in their series of three patients and also in another series of three patients by Chell and Quinnell (Chell & Quinnell, 2001).

Fusion in situ without decompression
Posterolateral fusion with or without instrumentation but without decompression has been described, and there is evidence in the literature to show that fusion alone without decompression results in relief of both back and leg pain. Ekman et al showed that there is significant improvement in patients who had surgical fusion with or without instrumentation compared to patients managed by exercise treatment alone in a prospective randomised controlled trial at an average follow-up of 9 years (Ekman et al, 2005).

Insitu fusion has the disadvantage of not correcting the sagittal imbalance and hence may give poor cosmetic result. However, this is disputed often in the literature with long-term follow-up studies where patients are little concerned about the cosmetic appearance of the sagittal plane deformity. However, there are other issues like a high prevalence of pseudoarthrosis (20-40%) in the literature and there are cases where there was cauda equine syndrome following a fusion in situ. Further, it is associated with progression of the slip.

Gaines procedure
This involves two stages with anterior L5 vertebrectomy as the first stage and then, followed by removal of the posterior elements of L5 as a second stage along with reduction of L4 on S1 and instrumented fusion (Gaines & Nichols). This was associated with a 75% early neurological deficit followed by a 25-30% of permanent L5 neurological deficit (Lehmer et al).

In general high grade slips are managed operatively. Decompression and fusion achieves good results, and care should be taken to avoid neurological deficit especially when attempting reduction of the listhesis.

Address for Correspondence:
P Lakshmanan
36, Greenhills
NE12 5BB


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