Back and leg pain due to a lumbar herniated nucleus pulposus creates a desperate, anxious patient. Such patients have been medically treated with analgesics, physical therapy, and, occasionally, epidural steroids.
Medical treatment alone is not always effective for treating large herniations, and surgical excision of the affected disk alone frequently results in vertebral instability, disk space collapse, and facet arthroplasty.
To prevent such potential sequelae, the Jones technique has been developed, performed, and studied. This technique is a modification of a soft posterior lumbar interbody fusion (PlJF). Sixty-six patients were followed for 2 years after this procedure to document disk height changes, pain scores, and functional ability.
The PLTJF was first developed and performed by Ralph Cloward, MD, in 1943 and published in 1953.1 Cloward advocated a combined disk removal and interbody fusion with the use of cortical and cancellous bone grafts in the interbody space to replace the removed disk.
Due to the procedure's technical difficulty, it was not universally performed. In the mid-1980s, Paul Lin, MD, revived interest in the PLIF among neurosurgeons and orthopedic surgeons. To increase awareness of the procedure, Lin performed several live telecasts of a modified Cloward procedure.2
For the best results using the procedure, Lin advocated stability of the PLfF construct and used large amounts of bone graft to achieve adequate ability to grow new bone within the intervertebral space.3
The most recent PLIF modifications and techniques rely heavily on the use of metallic cages, plates, and screws. Many studies of the current PLIF with cages maintain high fusion rates, but Agazzi et al4 found in their retrospective study that even though PLIF with cage fusion rates were 90%, the overall patient satisfaction rate was only 66%.
They found that there was no advantage in the use of cages over the traditional PLIF in terms of clinical success. In fact, they found that radiological fusion did not always equate to clinical success.4 Lin noted that the use of cages doubled the time necessary (from 6 months to 12 months) to radiologicalIy note a successful PLIF.3
The use of cages and other instrumentation is not without disadvantages. Cage failure has been reported in 3%-10% of the patients studied, with most failures due to migration, collapse, or slippage.4 Cage surgery also takes longer and adds approximately 50%- 100% more in costs. Whereas a traditional PLIF failure can be revised easily with instrumentation, an instrumented PLIF failure is more difficult to repair and revise.3*5
Figure 1 . A combination of OsteoSet Pellets, decompression bone, and autologous growth factor.
Figure 2. This magnetic resonance image demonstrates a typical candidate for the Jones technique of the soft posterior lumbar interbody fusion using decompression bone, calcium sulfate pellets, and autologous growth factor.
All of the PLIF procedures rely on the use of either autologous or allographs bone graft.410 Autologous bone grafts are taken during surgery from the iliac crest. Although this bone offers the most potential for osteogenesis and is a successful graft, there are numerous disadvantages. Pitfalls include graft site morbidity, limited availability, extended surgical time, and increased blood loss.2,7,1114
Some advocate the use of laminar decompression bone as the autologous bone graft material,15 but this may not produce enough bone to fill the void left by the removed disk.
AJlografts are another possibility, but the disadvantages include transmission of the disease, triggering of immunologic reactions, decreased graft strength, and lack of osteogenic potential.2·7·14
To alleviate the dependence of only autologous or allographic bone, many osteoconductive materials have recently been introduced. One of these materials, calcium sulfate (CaSO4), has been used in this study.
CaSO4 originates from gypsum and is commonly known as plaster of Paris. Not new to medicine, CaSO4 has been used for more than 100 years to fill bone defects and is readily accepted in human tissue.2,16
CaSO4 has been proven beneficial because it does not activate an immunologic response or inhibit osteogenesis. CaSO4 is absorbed at a constant rate and contributes to a rapid healing time.16 Because it is a biocompatible material, CaSO4 is highly suitable for use in the PLIF procedure and will not cause nerve root irritation even if in contact with dural membranes.
The area created by the excision of the disk material creates a central space where bone growth can take place.2 While CaSO4 is osteoconductive, it is not osteogenic or osteoinductive.
Osteogenesis occurs as new bone is synthesized by osteoprogenitor cells at the site of fusion. Autologous growth factors provide osteoinduction to the process because certain growth factors activate mesenchymal cells to stimulate bone growth.2,17 Studies have proven that when bone containing the mesenchymal cells and growth factors is introduced into a space with a biomaterial framework, extensive bone formation occurs.2,17,18
Vascularization through angiogenesis takes -place within this created space. The CaSO4 is gradually resorbed and presumably replaced by the patient's own bone, creating an equivalent amount of bone in comparison to autografts.2,9,18
Alexander et al13 evaluated CaSO4 used in spinal fusions. They found that the pellets were not radiologically visible at the 6-month follow-up. This suggested complete resorption. The researchers concluded that the use of CaSO4 pellets plus decompression bone offered a viable alternative to the use of autologous bone grafts in posterolateral and lumbosacral spinal fusion.
The Jones technique differs from the aforementioned procedures in that it is a soft PLIF, and it is not intended to fuse the lumbar spine. The value of the Jones technique comes from a bony bar that forms in the intervertebral space and acts as a barrier to significant disk space collapse and preserves facet joints.
The original Cloward PLIF procedure used a considerable amount of bone and required almost complete removal of the nucleus pulposus. Endplate disruption of vertebral bodies was performed with the ultimate goal of complete vertebral fusion. The Jones technique removes only the fragmented pieces of the nucleus pulposus centrally and leaves the annulus intact, excluding the incision site.
This investigation hypothesizes that the Jones technique, which uses CaSO4 pellets (OsteoSet, Wright Medical Technology, Ine, Arlington, Tenn), decompression bone, and autologous growth factors (lnterpore Cross International, Irvine, Calif), provides a radiological and clinically successful procedure without the use of a cage device and autologous iliac bone, thereby reducing pain, morbidity, hospital stay, and cost.
Materials and Methods
Sixty-six patients with large herniated disks underwent posterior lumbar interpositional arthroplasty (soft PLIF) at a total of 76 levels using the Jones technique of autologous decompression bone, CaSO4 pellets, and autologous growth factors (Figure 1). Patients were followed for 2 years. Of the 66 patients included in the study, 36 were women and 30 were men. The average patient age was 42 years, with a range from 21 to 78 years. The average patient weighed 178 lbs, with a range of 88 to 284 lbs. Average body mass index (BMl) was 25 for women and 37 for men.
All patients preoperatively showed evidence of extruded disk herniations by magnetic resonance imaging (Figure 2). Plain film radiographs showed no significant facet joint hypertrophy and normal or only slightly reduced disk space heights. A lumbar laminectomy and diskectomy were performed on each patient. Locally harvested autologous bone was cleaned of all extraneous tissue and morselized into 1- to 2-mm pieces using the technique published by Simmons.15 Approximately 2 cc of this decompression bone was then packed into the anterior disk space, along with 1 .25 cc of 3-mm CaSO4 pellets.
Autologous growth factors (AGFs) were obtained in the operative suite using the Interpore platelet aggregate filter. This technique yielded concentrated AGF, which was injected into the disk space after the placement of the bone and pellets.
Postoperatively, the patients were fitted with a modified thoracolumbar spinal orthosis and were allowed to ambulate. Bracing continued for 3 months. All patients were instructed to use a bone growth stimulator with a pulsed electromagnetic field (Orthofix International NV, Netherlands) for 4 hours daily for 3 to 4 months. All participants were encouraged to walk 1/2 mile by the end of first week postoperative. The distance was gradually increased to 3 miles by 1 month postoperative.
Radiographic data were obtained on all patients. Anteroposterior and lateral plain film radiographs were taken preoperatively and postoperatively at 1 , 3, 6, 12, and 24 months. All radiographs were evaluated and visually scored on a maturation scale of 1-3 by the senior author. AU radiographs were blinded as to time interval and patient. The radiographs were repeatedly recycled throughout the grading process to ensure reproducibility and accuracy of grading.
Figure 3. Six-month postoperative anteroposterior (A) and lateral (B) radiographs of a patient who underwent posterior lumbar interbody fusion at the L4-L5 level. This patient received a maturation score of 1 .
A maturation score of 1 represented >50% of the disk space filled with a homogenous bony mass, 2 represented <50% of the disk space filled without a homogenous bony mass, and 3 represented no visible bony material present in the disk space. Anterior and posterior disk height were measured at each interval on the plain lateral radiographs. The disk height was measured in millimeters as the distance between the end plates of the treated segments at the anterior and posterior borders. An analog linear pain scale with a range from 1-10 was completed at each visit (Figure 3).
One patient was treated at the L3L4 level, 32 patients were treated at L4-L5, and 23 patients were treated at L5-S1. Ten patients had a two-level soft PLIF at L4-L5 and L5-S1. The patient receiving the L3-L4 procedure was 45 years old with a BMI of 25. The average age of patients who underwent the procedure at L4-L5 was 44.5 years with an average BMI of 29.3. Patients with an L5-S1 procedure had an average age of 42.8 years with an average BMI of 25.7. The patients receiving a two-level soft PLIF procedure were the youngest with an average age of 36.4 years and an average BMI of 27.
No surgical or immediate postoperative complications were noted. The average length of hospital stay was 1.4 days, ranging from 1 to 4 days. One patient required, followup hospitalization following a fall, but the pain resolved. Nine patients had previously undergone a lumbar laminectomy prior to the soft PLIF. Two patients had received a laminectomy with posterolateral fusion below the soft PLIF level. Four patients had prior chemonucleolysis, three patients had prior intradiskal electrothermal therapy, and five patients had prior endoscopic procedures.
Intradiskal bone maturation varied, but maximal growth was achieved at an average of 5.2 months with no regressions noted on follow-up studies. Final maturation scores at 24 months revealed 42% of patients scoring a 1, 51% of patients scoring a 2, and 7% of patients scoring a 3 (Figure 4). No significant differences were noted in back and leg pain between those groups scoring a 1 or 2.
Of the patients in maturation group 3, five patients (7%) required additional surgery and underwent an instrumented posterolateral fusion (three smokers and two nonsmokers) 11-21 months after the initial interpositional arthroplasty.
Figure 4. Final maturation scores at 24 months revealed 42% of patients scoring a 1, 51% of patients scoring a 2, and 7% of patients scoring a 3. No significant differences were noted in back and leg pain between groups scoring a 1 or 2.
Figure 5. Analog pain scales preoperatively reflected average back pain to be 7.6 and leg pain 7.1
Analog pain scales preoperatively reflected average back pain to be 7.6 and leg pain 7.1 (Figure 5). Preoperative back pain by operative level was 8 for L3-L4, 7.28 for L4-L5, 7.65 for L5-S1, and 7.5 for L4-L5 and L5-S1. Preoperative leg pain by operative level was 10 for L3-L4, 7.31 for L4-L5, 6.65 for L5-S I , and 6.4 for L4-L5 and L5-S 1 .
Postoperative analog pain scales at 3 months reflected an average back pain of 3.0 (a reduction of 60%) and leg pain of 1.2 (a reduction of 83%). At 12 months, back pain had further been reduced to 2.6 (total reduction of 66%) and leg pain to 0.9 (total reduction of 87%). At 2 years, the back pain was 2.2 (total reduction of 71%) and leg pain was 0.7 (total reduction of 90%).
Anterior and posterior disk height was measured preoperatively in millimeters on lateral films. Average disk space height reduction at 2 years was 31.6%, but lordosis was preserved and joint motion was protected.
Herniations of the nucleus pulposus in the lumbar region are a common condition that can be treated either medically or surgically. If surgery becomes necessary, there are a variety of surgical options, including the original Cloward PLIF procedure and PLIF modifications that use metallic cages, plates, screws, and other instrumentation.
However, the aforementioned procedures do not come without disadvantages. Cage failure has been reported in 3%-10% of the cases studied, with most failure due to migration, collapse, or slippage.4 Surgery with instrumentation also takes longer and costs approximately $2,500 to $5,000 more than traditional PLIF. Whereas a traditional PLIF failure can be revised with instrumentation, an instrumented PLDF failure is more difficult to repair and revise.3,5
Furthermore, all of the PLIF procedures, including those with instrumentation, rely on the use of bone graft. The iliac crest is the most common graft site. Although this bone offers the most potential for osteogenesis and is successful as a graft, there are disadvantages. Drawbacks include graft site morbidity, limited availability, extended surgical time, and increased blood loss.2,7,12*14
Some researchers advocate the use of decompression bone only as the autologous bone graft material,15 but this may not produce enough bone to fill the void left by the removed disk. Allografts are another possibility, but there are disadvantages, including transmission of disease, the triggering of immunologic reactions, decreased graft strength, and the inability for osteogenesis.2,7,14
The Jones technique of the soft PLIF using decompression bone, CaSO4 pellets, and autologous growth factors provides excellent reduction of pain, stabilizes the disk space height with joint preservation, and is accomplished with minimal hospital stay, reduced costs, and morbidity. No complications occurred in any of the patients included in our study.
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