Eur Spine J (2003) 12 : 173–177
`DOI 10.1007/s00586-001-0376-4
`
`ORIGINAL ARTICLE
`
`Jie Zhao
`Tiesheng Hou
`Xinwei Wang
`Shengzhong Ma
`
`Posterior lumbar interbody fusion
`using one diagonal fusion cage
`with transpedicular screw/rod fixation
`
`Received: 15 December 2000
`Revised: 9 November 2001
`Accepted: 13 November 2001
`Published online: 11 January 2003
`© Springer-Verlag 2003
`
`J. Zhao · T. Hou · S. Ma
`Orthopedic Surgery Department,
`Changhai Hospital, 174 Changhai Road,
`Shanghai 200433, P.R. China
`X. Wang (✉
`)
`Orthopedic Department,
`Changzheng Hospital, 415 Feng yang
`Road, Shanghai, 200003, P.R. China
`e-mail: orth.wang@263.net,
`Tel.: 86-21-25071456,
`Fax: 86-21-25070583
`
`Abstract Posterior lumbar interbody
`fusion (PLIF) using threaded cages
`has gained wide popularity for lum-
`bosacral spinal disease. Our biome-
`chanical tests showed that PLIF using
`a single diagonal cage with unilateral
`facetectomy does add a little to spinal
`stability and provides equal or even
`higher postoperative stability than
`PLIF using two posterior cages with
`bilateral facetectomy. Studies also
`demonstrated that cages placed using
`a posterior approach did not cause the
`same increase in spinal stiffness seen
`with pedicle screw instrumentation,
`and we concluded that cages should
`not be used posteriorly without other
`forms of fixation. On the other hand,
`placement of two cages using a poste-
`rior approach does have the disadvan-
`tage of risk to the bilateral nerve
`roots. We therefore performed a pro-
`spective study to determine whether
`PLIF can be accomplished by utiliz-
`ing a single diagonal fusion cage with
`the application of supplemental
`transpedicular screw/rod instrumenta-
`tion. Twenty-seven patients under-
`went a PLIF using one single fusion
`cage (BAK, Sulzer Spine-Tech, Min-
`neapolis, MN, USA) inserted postero-
`laterally and oriented anteromedially
`on the symptomatic side with unilat-
`eral facetectomy and at the same
`level supplemental fixation with a
`transpedicular screw/rod system. The
`internal fixation systems included 12
`SOCON spinal systems (Aesculap
`AG, Germany) and 15 TSRH spinal
`systems (Medtronic Sofamor Danek,
`USA). The inclusion criteria were
`grade 1 to 2 lumbar isthmic spondy-
`lolisthesis, lumbar degenerative
`spondylolisthesis, and recurrent lum-
`
`bar disc herniations with instability.
`Patients had at least 1 year of low
`back pain and/or unilateral sciatica
`and a severely restricted functional
`ability in individuals aged 28–55
`years. Patients with more than grade
`2 spondylolisthesis or adjacent-level
`degeneration were excluded from the
`study. Patients were clinically as-
`sessed prior to surgery by an indepen-
`dent assessor; they were then re-
`assessed at 1, 3, 6, 12, 18, and 24
`months postoperatively by the same
`assessor and put into four categories:
`excellent, good, fair, and poor. Opera-
`tive time, blood loss, hospital ex-
`pense, and complications were also
`recorded. All patients achieved suc-
`cessful radiographic fusion at 2 years,
`and this was achieved at 1 year in 25
`out of 27 patients. At 2 years, clinical
`results were excellent in 15patients,
`good in 10, fair in 1, and poor in 1.
`Regarding complications, one patient
`had a postoperative motor and sen-
`sory deficit of the nerve root. Reoper-
`ation was required in one patient due
`to migration of pedicle screws. No
`implant fractures or deformities oc-
`curred in any of the patients. PLIF us-
`ing diagonal insertion of a single
`threaded cage with supplemental
`transpedicular screw/rod instrumenta-
`tion enables sufficient decompression
`and solid interbody fusion to be
`achieved with minimal invasion of
`the posterior spinal elements. It is a
`clinically safer, easier, and more eco-
`nomical means of accomplishing
`PLIF.
`
`Keywords Lumbar · Fusion cage ·
`Implant · Transpedicular screw ·
`Interbody
`
`

`

`174
`
`Introduction
`
`Posterior lumbar interbody fusion (PLIF), introduced by
`Dr. Ralph Cloward in the 1940s [2], laid the foundations
`for future biomechanically ideal fusion. A successful
`PLIF has the advantages of restoring the disc height, im-
`mobilizing the unstable degenerated intervertebral disc,
`decompressing the dural sac and the nerve roots, and
`restoring load-bearing to anterior structures [1]. Numer-
`ous techniques have been described, including use of au-
`tologous iliac crest bone graft, allograft bone, dowel-
`shaped graft, key stone graft, tricortical graft, and bone
`chips. Threaded-cage PLIF has the advantages of mini-
`mizing complications of graft resorption and disc space
`collapse and has therefore been recommended [5, 7].
`The PLIF method that was introduced involving im-
`plantation of two threaded cages [4, 7] lacked supplemen-
`tal internal fixation with a pedicle screw system. Insertion
`of one anterior or lateral cage has been successful on a
`limited basis. It is challenging to insert two cages of ap-
`propriate size posteriorly during the surgical procedure
`without extensive laminectomy and bilateral facetectomy.
`From a mechanical point of view, posterior element defi-
`ciencies adversely affect the stiffness of intervertebral fu-
`sion cages immediately after insertion, as these structures
`provide resistance to flexion and torsion. In addition,
`there is the obvious potential for neurological damage
`during surgery [8].
`The results of our biomechanical tests show that the
`posterolateral single threaded cage PLIF with unilateral
`facetectomy led to significantly higher postoperative stiff-
`ness than PLIF using two cages with bilateral facetectomy
`in pure compression, left bending, and left and right tor-
`sion. Flexion and extension loading modes also showed
`stiffer values in the single-cage group than in the two-
`cage group, but this was not statistically significant [9].
`We therefore decided to perform PLIF utilizing a single
`diagonal cage with the application of supplementary trans-
`pedicular screw/rod instrumentation while maintaining
`minimal invasion of the posterior elements. This study
`concerns the first 27 patients who have reached the 2-year
`follow-up interval.
`
`Patients and methods
`
`From July 1997 to August 1998, 27 patients with symptomatic
`lumbar disease were treated by PLIF using single BAK (Bagby
`and Kuslich) and additional pedicle screw internal fixation. Nine
`patients with grade 1 to 2 lumbar isthmic spondylolisthesis, 11 with
`lumbar degenerative spondylolisthesis, and 7 with recurrent lum-
`bar disc herniations with instability were treated prospectively.
`The internal fixation systems included 12 SOCON spinal systems
`(Aesculap AG, Germany) and 15 TSRH spinal systems (Medtronic
`Sofamor Danek, USA). There were 16 men and 11 women. The
`mean age was 46 years (range, 28–55 years). The minimum fol-
`low-up for review of 24 months.
`
`Table 1 Data on 27 patients
`
`Patients (n)
`Average age (years)
`Sex
`Male (n)
`Female (n)
`Average blood loss (ml)
`Average surgery time (min)
`Average hospital stay (days)
`Average hospital costs
`(US dollars)
`
`IS
`
`9
`43±8
`
`DS
`
`11
`50±3
`
`RDH
`
`7
`47±5
`
`7
`2
`711±105
`201±31
`14±2
`4975±318
`
`2
`9
`891±274
`225±72
`12±3
`4872±459
`
`2
`5
`1000±327
`225±56
`13±2
`4872±459
`
`IS, isthmic spondylolisthesis; DS, degenerative spondylolisthesis;
`RDH, recurrent disc herniation.
`
`Table 2 Pre- and postoperative data on 27 patients
`
`Preoperative
`
`Postoperative
`
`Symptoms
`Low back pain (n)
`Intermittent claudication (n)
`Leg pain (n)
`Fitness for work
`Disability (n)
`Partial disability (n)
`Restricted duty (n)
`Return to previous work (n)
`Clinical results
`Poor (n)
`Fair (n)
`Good (n)
`Excellent (n)
`
`Inclusion criteria
`
`27
`6
`12
`
`7
`15
`5
`0
`
`16
`10
`1
`0
`
`8
`2
`2
`
`0
`2
`10
`15
`
`0
`2
`10
`15
`
`The inclusion criteria were grade 1 to 2 lumbar isthmic spondy-
`lolisthesis, lumbar degenerative spondylolisthesis, and recurrent
`lumbar disc herniations with instability. Patients had at least 1 year
`of low back pain and/or unilateral sciatica and a severely restricted
`functional ability in individuals under 60 years of age. The preop-
`erative data on all 27 patients are shown in Table 1 and Table 2.
`
`Exclusion criteria
`
`The exclusion criteria included active infection, osteopenia, symp-
`tomatic vascular disease, active malignancy, gross obesity, greater
`than grade 2 spondylolisthesis, adjacent level degeneration, and
`pregnancy.
`
`Surgical technique
`
`The patient was placed in the kneeling/sitting position on an An-
`drew’s frame under general anesthesia. The surgical procedure is
`illustrated in Fig. 1. For patients with stenosis, unilateral laminec-
`
`

`

`175
`
`Fig. 1A–E Demonstration of the surgical procedure of posterior
`lumbar interbody fusion (PLIF) using one diagonal fusion cage
`with transpedicular screw fixation. A An appropriate hemi-laminec-
`tomy and unilateral partial facetectomy of the symptomatic side
`was performed, and pedicle screws were inserted bilaterally. B The
`disc space was then cleaned and the distraction plug gradually in-
`serted until the desired annular tension was achieved. C A single
`rod was applied to the contralateral side of the distraction plug, and
`locking nuts were tightened to maintain distraction. D After bone
`grafting, the BAK was inserted diagonally; finally, the second rod
`was put in place, and all the nuts were tightened. E Cross-section
`of extra bone graft previous to the BAK (Bagby and Kuslich) in-
`sertion
`
`tomy and facetectomy of the symptomatic side was able to achieve
`adequate decompression of the stenosis. For patients with spondy-
`lolisthesis, sequential distraction until the desired annular tensions
`were achieved was able to reduce slippage to some extent. Before
`cage insertion, the bone from laminectomy was grafted into the
`prepared disc space, while the iliac bone graft was placed in the
`cage. We believe that the bone outside the cage has greater fusion
`potential than the bone inside.
`X-rays or fluoroscopic images were taken in both the antero-
`posterior and lateral planes. The size of the implanted cage was de-
`termined by both the templates for X-ray, computed tomography
`(CT) or magnetic resonance imaging (MRI) scans and the extent of
`distraction during surgery.
`Patients’ clinical symptoms were assessed prior to surgery by
`an independent assessor (the third author) and reassessed at 1, 3, 6,
`12, 18, and 24 months postoperatively by the same assessor; pa-
`tients were put into four categories: excellent, good, fair, and poor.
`Clinical results were rated as excellent if the patient was pain-free
`and had returned to work at their previous occupation. If the pa-
`tient continued to have mild backache requiring non-narcotic med-
`ication only and had returned to full-time work, the results were
`rated as good. A fair result indicated that the patient’s continuing
`back pain prevented him or her returning to work or narcotic med-
`ication was required. A poor result indicated that the patient’s con-
`dition was worse than it was preoperatively or required additional
`surgery at the same level [10]. Operative time, blood loss, and hos-
`pital expense were also recorded (Table 1).
`Fusion status was determined from the anteroposterior, lateral,
`and flexion–extension radiographs. All radiographs were reviewed
`by the blinded assessor (the forth author), who determined whether
`there was radiographic fusion or nonunion. For a fusion to be
`deemed solid, the anteroposterior or lateral radiograph had to show
`mature bony trabeculae bridging the fusion area. Flexion–exten-
`sion films were considered to show fusion with less than 2° of mo-
`tion on the lateral film. Fusion results were purely determined by
`radiographic means [3].
`
`Results
`
`All patients achieved successful radiographic fusion at
`2 years, and 25 out of 27 patients at 1 year (Fig. 2). Clini-
`cal results at 2 years were excellent in 15 patients, good in
`10, fair in 1, and poor in 1 (reoperation). Ten patients were
`able to return to work, but not to their previous occupa-
`tion. Fifteen patients worked in their previous occupation.
`From a functional point of view, 12 patients had a mild
`level of low back pain, intermittent claudication, or sciat-
`ica, while 15 patients had no pain (Table 2). Regarding
`complications, one patient had a postoperative temporary
`motor and sensory deficit of the adjacent nerve root. Re-
`operation was required in one patient due to migration of
`pedicle screws. No implant fractures or deformities oc-
`curred in any of the patients.
`
`Discussion
`
`PLIF using threaded cages has gained wide popularity for
`lumbosacral spinal disease. Although many studies have
`concluded that threaded cages provide the same amount
`of stabilization as a PLIF bone graft with supplementary
`transpedicular screws/rod constructs, controversy still ex-
`ists [6, 9]. The threaded fusion cages were originally de-
`signed to be placed anteriorly; they have also been used
`from a posterior lumbar approach, which often involves
`removal of much of the facet joints to allow safe implan-
`tation. Our biomechanical test [9] showed that PLIF using
`a single diagonal cage with unilateral facetectomy does
`add a little to spinal stability, but it provides equal or even
`higher postoperative stability than PLIF using two poste-
`rior cages with bilateral facetectomy. Tencer et al. [8] also
`found that posterior placement of an insert can compro-
`mise the facet and lamina structures by reducing torsion
`stiffness, which is further reduced when two inserts are
`used. They believe that these data can be interpreted as in-
`dicating that it may be better to use a single insert rather
`than two.
`Oxland et al. [6] demonstrated that cages placed from
`both anterior and posterior directions provided good sta-
`bility in flexion, but not in extension. Supplementary pos-
`
`

`

`176
`
`Fig. 2 A A 41-year-old man with symptomatic grade 1 isthmic
`spondylolisthesis. B He was treated with posterior lumbar inter-
`body fusion (PLIF) using one diagonal BAK cage with unilateral
`facetectomy and with transpedicular screw fixation. C The result
`at 2-year follow-up. D The lateral radiograph at 2-year follow-up
`showed bony trabeculae bridging the fusion level
`
`terior fixation with pedicle or translaminar screws sub-
`stantially improves stability in all directions. On the other
`hand, placement of two cages from a posterior approach
`does have the disadvantage of risk to the bilateral nerve
`
`roots [4, 7]. Since posteriorly placed interbody fusion
`cages offer no significant increase in stiffness, their use as
`a stand-alone device may not be appropriate.
`This method has some obvious advantages. It is an eas-
`ier technique compared to routine two-cage PLIF. In treat-
`ment of patients with unilateral sciatica, the cage can be
`placed from the symptomatic side so as to avoid retraction
`of the nerve root and dural sac of the asymptomatic side.
`Since the application of the supplementary instrumenta-
`tion can provide adequate postoperative stability immedi-
`ately, an undersized cage can be used without worrying
`about its displacement. Regarding surgical procedure, sin-
`
`

`

`177
`
`gle-cage PLIF also has the advantages of less blood loss,
`shorter surgery time, and a shorter hospital stay.
`Indications for PLIF using single threaded fusion cages
`with supplementary instrumentation in lumbar spine have
`not yet been fully established or proved by long-term out-
`come studies. They might include degenerative or less
`than grade 2 isthmic spondylolisthesis after completion of
`a decompressive laminectomy, iatrogenic instability after
`previous decompressive procedures, and certain cases of
`
`retrolisthetic instability with disc space collapse and restora-
`tion of alignment.
`We conclude that PLIF using diagonal insertion of a
`single threaded cage with supplementary transpedicular
`screw/rod instrumentation enables sufficient decompres-
`sion and solid interbody fusion to be achieved, while
`maintaining minimal invasion to the posterior elements. It
`is a clinically safer, easier, and more economical way of
`achieving PLIF.
`
`References
`
`1. Bagby GW (1988) Arthrodesis by the
`distraction-compression method using
`a stainless steel implant. Orthopedics
`11:931–934
`2. Cloward RB (1953) The treatment of
`ruptured lumbar intervertebral discs by
`vertebral body fusion. Indications, op-
`eration technique, after care. J Neuro-
`surg 10:154–168
`3. Herkowitz HN, Kurz LT (1991) De-
`generative lumbar spondylolisthesis
`with spinal stenosis. J Bone Joint Surg
`[Am] 73:802–808
`
`4. Kuslich SD, Danielson G, Dowdle JD,
`Sherman J, Fredrickson B, Yuan H,
`Griffith SL (2000) Four-year follow-up
`results of lumbar spine arthrodesis us-
`ing the Bagby and Kuslich lumbar fu-
`sion cage. Spine 25:2656–2662
`5. Kuslich SD, Ulstrom CL, Griffith SL,
`Ahern JW, Dowdle JD (1998) The
`Bagby and Kuslich method of lumbar
`interbody fusion. History, techniques,
`and 2-year follow up results of a
`United States prospective, multicenter
`trial. Spine 23:1267–1278
`6. Oxland TR, Lund T (2000) Biome-
`chanics of stand-alone cages and cages
`in combination with posterior fixation:
`a literature review. Eur Spine J
`Suppl:S95–101
`
`7. Ray CD (1997) Threaded titanium
`cages for lumbar interbody fusions.
`Spine 22:667–679, discussion 679–680
`8. Tencer AF, Hampton D, Eddy S (1995)
`Biomechanical properties of threaded
`inserts for lumbar interbody spinal fu-
`sion. Spine 20:2408–2414
`9. Zhao J, Hai Y, Ordway NR (2000)
`Posterior lumbar interbody fusion us-
`ing posterolateral placement of a single
`cylindrical threaded cage. Spine 25:
`425–433
`10. Zdeblick TA (1993) A prospective,
`randomized study of lumbar fusion:
`preliminary results. Spine 18:983–991
`
`