The February 2024 Spine Roundup. 360. looks at: Surgeon assessment of bone – any good?; Robotics reduces radiation exposure in some spinal surgery; Interbody fusion cage versus anterior lumbar interbody fusion with posterior instrumentation; Is robotic-assisted pedicle screw placement an answer to the learning curve?; Acute non-traumatic spinal subarachnoid haematomas: a report of five cases and a systematic review of the literature; Is L4-L5 lateral interbody fusion safe and effective?

Polyetheretherketone (PEEK) interbody fusion cages combined with autologous bone graft is the current clinical gold standard treatment for spinal fusion, however, bone graft harvest increases surgical time, risk of infection and chronic pain. We describe novel low-stiffness 3D Printed titanium interbody cages without autologous bone graft and assessed their biological performance in a pre-clinical in vivo interbody fusion model in comparison to the gold standard, PEEK with graft. Titanium interbody spacers were 3D Printed with a microporous (Ti1: <1000μm) and macroporous (Ti2: >1000μm) design. Both Ti1 and Ti2 had an identical elastic modulus (stiffness), and were similar to the elastic modulus of PEEK. Interbody fusion was performed on L2-L3 and L4-L5 vertebral levels in 24 skeletally mature sheep using Ti1 or Ti2 spacers, or a PEEK spacer filled with iliac crest autograft, and assessed at 8 and 16 weeks. We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate. Functional spinal units were biomechanically tested to analyse range of motion, neutral zone, and stiffness. Results: Bone formation in macroporous Ti2 was significantly greater than microporous Ti1 treatments (p=.006). Fusion scores for Ti2 and PEEK demonstrated greater rates of bone formation from 8 to 16 weeks, with bridging rates of 100% for Ti2 at 16 weeks compared to just 88% for PEEK and 50% for Ti1. Biomechanical outcomes significantly improved at 16 versus 8 weeks, with no significant differences between Ti and PEEK with graft. This study demonstrated that macroporous 3D Printed Ti spacers are able to achieve fixation and arthrodesis with complete bone fusion by 16 weeks without the need for bone graft. These significant data indicate that low-modulus 3D Printed titanium interbody cages have similar performance to autograft-filled PEEK, and could be reliably used in spinal fusion avoiding the complications of bone graft harvesting

Aims

We compared the clinical and radiological outcomes of using a polyetheretherketone cage with (TiPEEK) and without a titanium coating (PEEK) for instrumented transforaminal lumbar interbody fusion (TLIF).

Transforaminal lumbar interbody fusion (TLIF) using an implanted cage is the gold standard surgical treatment for disc diseases such as disc collapse and spinal cord compression, when more conservative medical therapy fails. Titanium (Ti) alloys are widely used implant materials due to their superior biocompatibility and corrosion resistance. A new Ti-6Al-4V TLIF cage concept featuring an I-beam cross-section was recently proposed, with the intent to allow bone graft to be introduced secondary to cage implantation. In designing this cage, we desire a clear pathway for bone graft to be injected into the implant, and perfused into the surrounding intervertebral space as much as possible. Therefore, we have employed shape optimization to maximize this pathway, subject to maintaining stresses below the thresholds for fatigue or yielding.

The TLIF I-beam cage (Fig. 1(a)) with an irregular shape was parametrically designed considering a lumbar lordotic angle of 10°, and an insertion angle of 45° through the left or right Kambin's triangles with respect to the sagittal plane. The overall cage dimensions of 30 mm in length, 11 mm in width and 13 mm in height were chosen based on the dimensions of other commercially available cages. The lengths (l_a, l_p) and widths (w_a, w_p) of the anterior and posterior beams determine the sizes of the cage's middle and posterior windows for bone graft injection and perfusion, so they were considered as the design variables for shape optimization. Five dynamic tests (extension/flexion bending, lateral bending, torsion, compression and shear compression, as shown in Fig. 2(b)) for assessing long term cage durability (10⁷ cycles), as described in ASTM F2077, were simulated in ANSYS 15.0. The multiaxial stress state in the cage was converted to an equivalent uniaxial stress state using the Manson-Mcknight approach, in order to test the cage based on uniaxial fatigue testing data of Ti-6Al-4V. A fatigue factor (K) and a critical stress (σ_cr) was introduced by slightly modifying Goodman's equation and von Mises yield criterion, such that a cage design within the safety design region on a Haigh diagram (Fig. 2) must satisfy K ≤ 1 and σ_cr ≤ S_Y = 875 MPa (Ti-6Al-4V yield strength) simultaneously.

After shape optimization, a final design with l_a = 2.30 mm, l_p = 4.33 mm, w_a = 1.20 mm, w_p = 2.50 mm, was converged upon, which maximized the sizes of the cage's windows, as well as satisfying the fatigue and yield strength requirements. In terms of the strength of the optimal cage design, the fatigue factor (K) under dynamic torsion approaches 1 and the critical stress (σ_cr) under dynamic lateral bending approaches the yield strength (S_Y = 875 MPa), indicating that these two loading scenarios are the most dangerous (Table 1). Future work should further validate whether or not the resulting cage design has reached the true global optimum in the feasible design space. Experimental validation of the candidate TLIF I-beam cage design will be a future focus.

For any figures or tables, please contact authors directly (see Info & Metrics tab above).

The April 2013 Spine Roundup³⁶⁰ looks at: smuggling spinal implants; local bone graft and PLIF; predicting disability with slipped discs; mortality and spinal surgery; spondyloarthropathy; brachytherapy; and fibrin mesh and BMP.

A number of causes have been advanced to explain the destructive discovertebral (Andersson) lesions that occur in ankylosing spondylitis, and various treatments have been proposed, depending on the presumed cause. The purpose of this study was to identify the causes of these lesions by defining their clinical and radiological characteristics.

We retrospectively reviewed 622 patients with ankylosing spondylitis. In all, 33 patients (5.3%) had these lesions, affecting 100 spinal segments. Inflammatory lesions were found in 91 segments of 24 patients (3.9%) and traumatic lesions in nine segments of nine patients (1.4%). The inflammatory lesions were associated with recent-onset disease; a low modified Stoke ankylosing spondylitis spine score (mSASSS) due to incomplete bony ankylosis between vertebral bodies; multiple lesions; inflammatory changes on MRI; reversal of the inflammatory changes and central bony ankylosis at follow-up; and a good response to anti-inflammatory drugs. Traumatic lesions were associated with prolonged disease duration; a high mSASSS due to complete bony ankylosis between vertebral bodies; a previous history of trauma; single lesions; nonunion of fractures of the posterior column; acute kyphoscoliotic deformity with the lesion at the apex; instability, and the need for operative treatment due to that instability.

It is essential to distinguish between inflammatory and traumatic Andersson lesions, as the former respond to medical treatment whereas the latter require surgery.

The post-operative changes in the serum levels of CRP and serum amyloid A (SAA) were investigated prospectively in 106 patients after posterior lumbar interbody fusion. In 96 patients who did not have complications related to infection within the first year after operation, the median levels of CRP before operation and on days 3, 7 and 13 after were 0.02 (0.01 to 0.03), 9.12 (2.36 to 19.82), 1.64 (0.19 to 6.10) and 0.53 (0.05 to 2.94) mg/dl, respectively and for SAA, 2.6 (2.0 to 3.8), 1312.1 (58.0 to 3579.8), 77.3 (1.8 to 478.4), 14.1 (0.5 to 71.9) μg/ml, respectively. The levels on day 3 were the highest for both CRP and SAA and significantly decreased (p < 0.01) by day 7 and day 13.

In regard to CRP, no patient had less than the reference level (0.1 mg/dl) on day 7. In only three had the level decreased to the reference level, while in 93 it was above this on day 13. However, for SAA, the levels became normal on day 7 in 10 cases and on day 13 in 34 cases. The ratios relative to the levels on day 3 were significantly lower for SAA compared with CRP on day 7 and day 13. Of the ten patients with infection in the early stages, the level of CRP decreased slightly but an increase in SAA was observed in six.

We concluded that SAA is better than CRP as a post-operative inflammatory marker.

Introduction Anterior column reconstruction and fusion remains the gold standard of treatment for a number of spinal pathologies. One of the challenges of interbody fusions cages is the footprint of the cage reducing the surface area of endplate available for fusion. Biodegradable polymer implants will over time present a greater area for fusion and may help to reduce problems such as stress shielding, particulate debris and retained foreign body response. Resorbable cages have been have been prepared from a number of different materials, including inorganic composites (eg hydroxyapatite / tricalcium phosphate) and polymers (Poly L-lactide-co-D,L-lactide (PDLLA)). However all of the current options for interbody fusion have reported deficiencies or complications. The synthesis, mechanical properties, and degradation behaviour of two novel biopolymers are presented and the applicability for use as materials in interbody fusion devices is discussed. Methods Methacrylated adipic anhydride (MAA) and methacrylated sebacic anhydride (MSA) pre-polymers were synthesized by melt condensation. Conversion of the acid to the anhydride was confirmed using 1H nuclear magnetic resonance (NMR) (Bruker, Alexandria, NSW) and FT- Infrared spectroscopy (Nicolet, Waltham MA). These pre-polymers were subsequently co-polymerized with methyl methacrylate (MMA) and 0.25 wt% benzoyl peroxide at 65oC for 16hrs and post-cured at 120oC under vacuum for 2 hrs to form biodegradable networks. The co-polymerization behaviour was monitored by FT-Raman spectroscopy. The compressive mechanical properties of the polymer were determined using an Instron 5567 (Bayswater Vic.). The polymer networks were degraded in phosphate buffered saline (PBS) with various amounts of MAA and MSA. Results The formation of the pre-polymer was confirmed with the observation of NMR peaks at 5.8 and 6.2 ppm and FT-IR peaks at 1637cm-1. Copolymerization was followed with consecutive FT-IR acquisitions with 100% conversion achieved between 10 and 30 hrs depending on the ratio of MMA to MSA or MAA. Increasing the fraction of methacrylated anhydride slowed the reaction rate. The compressive strength of the MAA and MSA based copolymers was measured as a function of anhydride concentration. Compressive strength for MMA increased (90±9 to 140±10 Mpa) in an approximately linear manner for MAA concentrations from 10 to 40 wt.% but decreased markedly for MAA concentration of 45% (62±14 Mpa). The compressive strength of MSA decreased exponentially for concentrations ranging from 10 to 45 wt.% (140±18 to 39±1 Mpa). Discussion The use of poly-L-lactic acid in lumbar interbody cages has been shown to be mechanically feasible with the mechanical strength of the cage material reported to be 93 Mpa (. 1. ). The material described here has controlled mechanical properties in the required range as well as a degradation behaviour that lends itself better to spinal applications than current materials

Background: A 9- year-old child with osteogenesis imperfecta and severe cervical kyphosis associated with wedged vertebrae and progressive neurological deterioration is presented. There is no report of upper cervical kyphosis associated with wedged vertebrae in osteogenesis imperfecta in the literature. We discuss the methods and difficulties in the surgical management of this condition and to highlight the appropriate surgical approach. Methods: Methods:A 9-year-old girl presented with progressive cervical kyphosis and quadriparesis. At the age of 3 years she underwent posterior cervical fusion (C1–C6) for instability and deformity. Radiological and laboratory investigations confirmed the diagnosis of osteogenesis imperfecta. Radiographs of the cervical spine revealed a kyphotic deformity of 120° Magnetic Resonance Imaging (MRI) and Computerised Tomography (CT) scans showed anterior cord compression due to wedged vertebrae at C3 and C4. MRI-Angiography was performed pre-operatively to identify the anatomical position of the vertebral arteries. A modified anterolateral approach to the upper cervical spine was performed. Anterior C3 and C4 corpectomies with interbody fusion with cage and plate fixation was carried out. Results: Postoperatively the patient made a full neurological recovery and significant correction of the deformity was achieved and correction was maintained at final follow-up. Conclusion: Cervical kyphotic deformity in Osteogenesis Imperfecta is uncommon. Association of this condition with wedged vertebrae is rare. Surgical decompression of the upper cervical spine with severe kyphosis is a challenging problem. Which surgical approach should be used is controversial? There are difficulties exposing wedged vertebrae by a standard anterior or chin split approach to perform vertebrectomy. Costo-transversectomy has been used successfully in patients with Gibbous deformity in the thoracic spine but due the presence of vertebral artery in the cervical spine posterolateral approach is impossible. We have used a modified anterolateral approach to overcome this problem. Spinal stabilisation in children with Osteogenesis Imperfecta and poor bone quality is another challenge. We have used a small diameter MOSS cage with maxillofacial plate and screws to achieve stabilisation and fusion. The purpose of this report is to highlight the importance of diagnosis of progressive cervical kyphotic deformity in children with osteogenesis imperfecta and also to describe the difficulties encountered with surgical management of this condition

Purpose: Lumbar interbody fusion cages is a valid technique in the treatment of disc diseases. The aim of this study is to evaluate its validity through the analysis of clinical outcomes and radiological findings. Materials and methods: The paper reports a serie of 52 posterior lumbar interbody fusion cages operations. Clinical outcomes and radiological results were evaluated at a mean of 5 years post-surgery. Results: Outcome analysis showed a gradual improvement in symptoms. After surgery, the majority of patients returned to their normal activities. Follow-up plain roentgenograms showed no loss of disc height and no signs of implant’s looseness. Computed Tomography (CT) scans showed the presence of mineralized autologous bone grafts inside the interbody cages. Conclusions: Expandable interbody cages allow the restoration of the disc space height, giving support to the anterior column, opening the neuroforaminal area and providing increased stability. The interpretation of fusion on the basis of roentgenograms is subjected to arguement. Thin CT scan offers more information than X-rays about the fusion process

Background and purposes of study The objective of this study is to report the preliminary clinical data from a stand-alone interbody fusion cage (Stabilis™) from two centres. Methods and results This was a retrospective group comparative study. Anterior lumbar interbody fusion was performed using Brantigan (n=6) or Stabilis™ cages (n=19). Clinical assessment was performed using standardised questionnaires. Lumbar flexion/extension views were used to assess union and implant subsidence. There were no significant differences between the groups for ODI, VAZ, MZ and MSPQ pre-operatively. The Stabilis group showed an improvement in ODI (pre: 49.4; post: 39.3; p=0.024), VAS (pre: 76.1; post: 47.8; p< 0.01) and MZ (pre 32.9; post: 20.6; p< 0.01). There was no statistical improvement in the Brantigan cage group. Despite clinical improvement, five patients in the Stabilis group failed to unite and six demonstrated subsidence of the implant. The relationship between non-union and subsidence was statistically significant (p = 0.017). Furthermore, the change in ODI between patients who united and those who did not was both statistically significant (p=0.03) and the difference in mean ODI between the two groups was considerable (21%). Conclusions: Stand-alone cages show promise, involve a shorter operating time and less tissue trauma for the patient. This study has identified a high rate of non-union and implant subsidence. This did not appear to be clinically relevant

Introduction: Recent evidence from the Swedish Lumbar Spine Group has confirmed the anecdotal opinions of many spinal surgeons that fusion for persistent back pain can be a very effective treatment. However, it is clear that many more variables operate in determining clinical success than just radiological evidence of solid fusion. The very careful selection of patients for low back surgery is, in the opinion of the authors, the most important predictor of success. This paper addresses this issue and presents data to show why clinical failure can coexist with radiological success. Methods: Between October 1997 and January 2001, 3600 spinal fusion using Diapason pedicle screw instrumentation and Brantigan anterior interbody fusion cages was performed on 25 patients. During this period 5,850 new outpatients with back pain were assessed in the low back clinic. Patients were selected by the following criteria: Low back pain of two years or more duration; Pain resistant to all non-operative and minimally invasive treatments; Normal psychosocial profile; Normal body mass index; Non-Smokers; Single or two level disease on MRI proven to be painful by provocative discography; No current insurance or workers-compensation claims. Postal follow-up was at a minimum of 2 years post-surgery (mean 47 months) using the Low Back Outcome Score (LBOS) and x-rays taken at the two-year clinic follow-up were independently assessed to determine fusion. Results: 24 patients returned the questionnaire (96%). Only 20 (83%) patients had ‘good’ or ‘excellent’ results, as defined by the LBOS. However, 92% of patients stated that they would opt to have a circumferential fusion again, if guaranteed the same post-operative result. The same number of patients stated they would recommend the treatment to friend or family member. Analysis of the post-operative radiographs revealed that spinal fusion (as defined by the Brantigan and Steffee criteria) was present in all 25 cases. Conclusions: Our opinion that patient selection is the most important predictor of satisfactory outcome in spinal surgery is demonstrated in this study by the mismatch between the clinical and radiological results. We have identified the causes of clinical failure in this group of patients as: Multiple sites of musculoskeletal pain confounding the LBOS; Neuropathic leg pain that cannot respond to surgical treatment; More than two previous spinal operations; Excessive pre-operative disability and functional loss that confounds the LBOS; Poor psychosocial profile. Stringent application of rigid selection criteria might improve outcomes in lumbar spinal fusion so that clinical and radiological results correlate more closely. However, even with adherence to such rigid criteria, the outcome tool (LBOS) may be confounded and a more holistic assessment of outcome, including a more sensitive subjective assessment of satisfaction, might be a better measure

Introduction: The initial promise of stand-alone threaded anterior interbody fusion cages to treat chronic low back pain has not been maintained. In an attempt to overcome some of the problems associated with threaded fusion devices (endplate subsidence, failure to re-establish lordosis and displacement) a two-part ALIF cage was devised. The device consists of a rectangular frame that accommodates a threaded, open-weave cylinder holding bone graft material. The device addresses the biomechanical issues required for successful ALIF whilst providing a large area for bone in-growth and is a less invasive solution than a formal 3600 fusion. Methods: From August 2001 to December 2002, 41 patients who fulfilled selection criteria for a single or two-level 3600 spinal fusion for low back and leg symptoms underwent ALIF using Stabilis. All patients had failed to improve with all non-invasive and minimally invasive treatments available to them. Prospective follow-up has continued for all cases using the Low Back Outcome Score and a Patient Satisfaction Score. Plain x-rays were taken at 3, 6 and 12 months post-operatively and the 12-month series included flexion and extension films. Results: Ten patients (24.4%) have completed more than 12 months follow-up; 18 (43.9%) are between six and twelve months post surgery and the rest (31.7%) have less than six months follow-up. LBOS results for the first 10 showed 9 (90%) as excellent or good. LBOS results for the second group of 18 were excellent or good in 15 (83.3%). All but two of the 28 patients, would be prepared to undergo the procedure again and all would recommend the operation to a friend with similar trouble. Radiographic assessment at 6 months showed 16 patients had at least a partial anterior or posterior sentinel sign. Using motion criteria, all 10 cases at one year were fused on flexion and extension lateral x-rays. No devices migrated anteriorly or posteriorly and no lucent lines have been seen around the implants. Three of the two-level procedures showed some subsidence of the L4/5 implant into the L5 vertebral body, but none were symptomatic. No clear reasons have emerged to explain the clinical failure of 14% of the patients given the radiological success. In only one was there a mismatch in the LBOS outcome measure and the satisfaction rating. Conclusions: Stabilis is a useful standalone ALIF device that not only addresses the theoretical biomechanical failures of anterior threaded interbody fusion cages, but has been shown in this early clinical and radiological evaluation to be effective, objectively and subjectively. It is likely that in the medium term future, fewer patients will require fusion to treat back and leg pain as the results from lumbar spine arthroplasty become established and non-fusion technologies become accepted. Until that time, experience in the UK and USA suggests that Stabilis is a good alternative to 3600 fusion

Introduction: Discectomy for herniation of the nucleus pulposus is an effective procedure when conservative treatment has failed. However, a number of patients rapidly progress to symptomatic instability after discectomy. Those most likely to develop instability have central and multi-regional herniations. Therefore, primary posterior lumbar interbody fusion (PLIF) may be a better option than discectomy alone in this group. This paper presents the clinical and radiological outcome of a consecutive group of such patients treated in one centre by PLIF, but recognises that newer technologies may make such destructive spinal surgery unnecessary in the future. Methods: Between June 1997 and December 2000, PLIF for central disc herniation presenting with acute, subacute and chronic back and leg pain, with or without neurological loss, using Diapason pedicle screw instrumentation and Ogival PEEK (Polyether-ether-ketone) Interbody Fusion cages was performed on 41 patients. Eight patients presented acutely with cauda equina symptoms and 33 patients had sub-acute or chronic symptoms. Formal clinic follow-up was continued for at least two years post-surgery and the final outcome at 2 to 5 years after operation was assessed using the Low Back Outcome Score (LBOS). Two independent orthopaedic surgeons assessed the radiological evidence of fusion on X-rays taken at least two years after surgery. Results: 39 of the 41 patients completed the LBOS questionnaire (95%). One patient had died from an unrelated cause and the other could not be contacted having moved away. 34 (87%) of these had an excellent or good outcome according to the LBOS criteria. However, every patient who returned the questionnaire stated that they would undergo the operation again if guaranteed the same surgical result and all would recommend it to a friend for similar trouble. Four patients (9.7%) were dissatisfied with the process of care they experienced. Analysis of radiographs taken between two and four years post-operatively revealed that spinal fusion (as defined by the Brantigan and Steffee criteria) was present in 38 cases (92.7%). None of the patients with a non-union radiologically had a poor outcome. Conclusions: Post-discectomy instability causing disabling low back and leg pain is more likely to occur in patients with an incompetent annulus than those with a largely intact annulus. The patients in this series all had good evidence on MRI of complete (pan-annular) failure. The decision to perform an acute single level PLIF was taken after discussion with the patients, presenting them with the option of having only a central discectomy and a later fusion if needed or of dealing with the problem at one operation. The outcomes described in this study show that this condition is a good indication for PLIF. However, newer technologies such as disc arthroplasty may be a better option for this group of patients in the future

INTRODUCTION: The initial promise of stand-alone threaded anterior interbody fusion cages to treat chronic low back pain has not been maintained. In an attempt to overcome some of the problems associated with threaded fusion devices (endplate subsidence, failure to re-establish lordosis and displacement) a two-part ALIF cage was devised. The device consists of a rectangular frame that accommodates a threaded, open-weave cylinder holding bone graft material. The device addresses the biomechanical issues required for successful ALIF whilst providing a large area for bone in-growth and is a less invasive solution than a formal 360° fusion. METHODS: From August 2001 to December 2002, 41 patients who fulfilled selection criteria for a single or two-level 360° spinal fusion for low back and leg symptoms underwent ALIF using Stabilis. All patients had failed to improve with all non-invasive and minimally invasive treatments available to them. Prospective follow-up has continued for all cases using the Low Back Outcome Score and a Patient Satisfaction Score. Plain X-rays were taken at three, six and 12 months post-operatively and the 12-month series included flexion and extension films. RESULTS: Ten patients (24.4%) have completed more than 12 months follow-up; 18 (43.9%) are between six and twelve months post surgery and the rest (31.7%) have less than six months follow-up. LBOS results for the first 10 showed nine (90%) as excellent or good. LBOS results for the second group of 18 were excellent or good in 15 (83.3%). All but two of the 28 patients, would be prepared to undergo the procedure again and all would recommend the operation to a friend with similar trouble. Radiographic assessment at six months showed 16 patients had at least a partial anterior or posterior sentinel sign. Using motion criteria, all 10 cases at one year were fused on flexion and extension lateral X-rays. No devices migrated anteriorly or posteriorly and no lucent lines have been seen around the implants. Three of the two-level procedures showed some subsidence of the L4/5 implant into the L5 vertebral body, but none was symptomatic. No clear reasons have emerged to explain the clinical failure of 14% of the patients given the radiological success. In only one was there a mismatch in the LBOS outcome measure and the satisfaction rating. CONCLUSIONS: Stabilis is a useful stand-alone ALIF device that not only addresses the theoretical biomechanical failures of anterior threaded interbody fusion cages, but has been shown in this early clinical and radiological evaluation to be effective, objectively and subjectively. It is likely that in the medium term future, fewer patients will require fusion to treat back and leg pain as the results from lumbar spine arthroplasty become established and non-fusion technologies become accepted. Until that time, experience in the UK and USA suggests that Stabilis is a good alternative to 360° fusion

INTRODUCTION: Recent evidence from the Swedish Lumbar Spine Group has confirmed the anecdotal opinions of many spinal surgeons that fusion for persistent back pain can be a very effective treatment. However, it is clear that many more variables operate in determining clinical success than just radiological evidence of solid fusion. The very careful selection of patients for low back surgery is, in the opinion of the authors, the most important predictor of success. This paper addresses this issue and presents data to show why clinical failure can coexist with radiological success. METHODS: Between October 1997 and January 2001, 360° spinal fusion using Diapason pedicle screw instrumentation and Brantigan anterior interbody fusion cages was performed on 25 patients. During this period 5,850 new outpatients with back pain were assessed in the low back clinic. Patients were selected by the following criteria: Low back pain of two years or more duration; Pain resistant to all non-operative and minimally invasive treatments; Normal psycho-social profile; Normal body mass index; Non-Smokers; Single or two level disease on MRI proven to be painful by provocative discography; No current insurance or workers-compensation claims. Postal follow-up was at a minimum of two years post-surgery (mean 47 months) using the Low Back Outcome Score (LBOS) and X-rays taken at the two-year clinic follow-up were independently assessed to determine fusion. RESULTS: 24 patients returned the questionnaire (96%). Only 20 (83%) patients had ‘good’ or ‘excellent’ results, as defined by the LBOS. However, 92% of patients stated that they would opt to have a circumferential fusion again, if guaranteed the same post-operative result. The same number of patients stated they would recommend the treatment to friend or family member. Analysis of the post-operative radiographs revealed that spinal fusion (as defined by the Brantigan and Steffee criteria) was present in all 25 cases. CONCLUSIONS: Our opinion that patient selection is the most important predictor of satisfactory outcome in spinal surgery is demonstrated in this study by the mismatch between the clinical and radiological results. We have identified the causes of clinical failure in this group of patients as: Multiple sites of musculo-skeletal pain confounding the LBOS; Neuropathic leg pain that cannot respond to surgical treatment; More than two previous spinal operations; Excessive pre-operative disability and functional loss that confounds the LBOS; Poor psychosocial profile. Stringent application of rigid selection criteria might improve outcomes in lumbar spinal fusion so that clinical and radiological results correlate more closely. However, even with adherence to such rigid criteria, the outcome tool (LBOS) may be confounded and a more holistic assessment of outcome, including a more sensitive subjective assessment of satisfaction, might be a better measure

INTRODUCTION: Discectomy for herniation of the nucleus pulposus is an effective procedure when conservative treatment has failed. However, a number of patients rapidly progress to symptomatic instability after discectomy. Those most likely to develop instability have central and multi-regional herniations. Therefore, primary posterior lumbar interbody fusion (PLIF) may be a better option than discectomy alone in this group. This paper presents the clinical and radiological outcome of a consecutive group of such patients treated in one centre by PLIF, but recognises that newer technologies may make such destructive spinal surgery unnecessary in the future. METHODS: Between June 1997 and December 2000, PLIF for central disc herniation presenting with acute, sub-acute and chronic back and leg pain, with or without neurological loss, using Diapason pedicle screw instrumentation and Ogival PEEK (Poly-ether-ether-ketone) Interbody Fusion cages was performed on 41 patients. Eight patients presented acutely with cauda equina symptoms and 33 patients had sub-acute or chronic symptoms. Formal clinic follow-up was continued for at least two years post-surgery and the final outcome at two to five years after operation was assessed using the Low Back Outcome Score (LBOS). Two independent orthopaedic surgeons assessed the radiological evidence of fusion on X-rays taken at least two years after surgery. RESULTS: 39 of the 41 patients completed the LBOS questionnaire (95%). One patient had died from an unrelated cause and the other could not be contacted having moved away. 34 (87%) of these had an excellent or good outcome according to the LBOS criteria. However, every patient who returned the questionnaire stated that they would undergo the operation again if guaranteed the same surgical result and all would recommend it to a friend for similar trouble. Four patients (9.7%) were dissatisfied with the process of care they experienced. Analysis of radiographs taken between two and four years post-operatively revealed that spinal fusion (as defined by the Brantigan and Steffee criteria) was present in 38 cases (92.7%). None of the patients with a non-union radiologically had a poor outcome. CONCLUSIONS: Post-discectomy instability causing disabling low back and leg pain is more likely to occur in patients with an incompetent annulus than those with a largely intact annulus. The patients in this series all had good evidence on MRI of complete (pan-annular) failure. The decision to perform an acute single level PLIF was taken after discussion with the patients, presenting them with the option of having only a central discectomy and a later fusion if needed or of dealing with the problem at one operation. The outcomes described in this study show that this condition is a good indication for PLIF. However, newer technologies such as disc arthroplasty may be a better option for this group of patients in the future

Purpose: Interbody fusion cages have met with great success as an adjunct in the treatment of painful degenerative disc disease. One of the limitations is the need for the use of autogenous cancellous bone graft. In preclinical studies recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in a variety of carriers has been shown to be an effective substitute for autogenous bone, resulting in more rapid and reliable healing than that seen in control groups. The goal of this study was to report the early results of the first human trial attempting to use rhBMP-2 in interbody fusion cages. Methods: This study was an FDA approved IDE multicenter pilot study. From 1/97 to 4/97, 14 patients were entered into a prospective, randomized trial. All patients had single level lumbar degenerative disc disease that was refractory to prolonged nonoperative care and were candidates for anterior interbody fusion of L4-5 or L5-S1. After consent, patients were randomized to either the control group (N-3) and received autogenous bone inside tapered titanium fusion cages (NOVUS LT, Sofamor Danek Memphis, TN) or to the investigational group (N = 11) and received rhBMP-2 (1.5 mg/ml)(Genetics Institute, Cambridge MA) delivered in a collagen sponge (Helistat, Integra Life Sciences, Plainsboro, NJ) inside the fusion cages. Depending on the size, the sponge in each cage was soaked with from 1.3 to 2.6 ml of the rhBMP2 solution. Patients were followed at regular intervals with plain x-ray, CT scan with reconstruction, and a full panel of blood tests. Radiographs were reviewed by an independent blinded radiologist with fusion defined as < 5 degrees of sagittal motion, absence of radiolucent lines, and presence of continuous bone through the cages. Clinical results were assessed using an outcomes questionnaire including the SF-36 general health status and Oswestry low back specific instruments. Results: All 14 patients were available for 1-year follow-up. No cages displaced and no further surgeries were required. Mean hospital stay was 2.0 days for the rhBMP-2 patients compared to 3.3 days for the autograft controls. Of the 11 rhBMP2 patients, 10 of 11 were judged to be fused at 3 months. At 6 months and 1-year all 11 rhBMP-2 patients were noted to have a solid arthrodesis. Of the 3 control patients, 2 had solid arthodesis and one had an apparent nonunion at 1 year. On sagittal CT scan reconstruction new bone growth was seen throughout and anterior to the cages that were filled with rhBMP-2. No patients had bone formation outside of the desired area. The control patient with the nonunion had a halo surrounding the cage on the sagittal CT reconstruction. This patient had persistence of low back pain. Compared to preop, the Oswestry scores at 3 months were decreased in the rhBMP-2 group (39 to 30) compared to controls which were increased (35 to 43) and both mean scores were similar at 6 months (28 and 27). Conclusion: The preliminary results from this clinical trial with rhBMP-2 inside interbody fusion cages were excellent and support a larger pivotal trial. The arthrodesis was found to occur more rapidly and reliably than in the controls, although the sample size was limited. In addition to faster bone healing, a major advantage was the elimination of bone graft donor site morbidity and realization of decreased hospital stay. No evidence of excessive bone formation or systemic complications occurred. Moreover, this study provides one of the first demonstrations of consistent and unequivocal osteoinduction by a recombinant growth factor in humans

Introduction: The nonunion rate is higher and loss of reduction is common after reduction and fusion for the higher grades of spondylolisthesis. This is due to fusion bone base deficiency and lack of anterior column support, and can be addressed by supplementing the posterolateral fusion with a posterior lumbar interbody fusion (PLIF). Materials: All patients had a single disc level degenerative or spondylolytic slip exceeding 25%. Laminectomy and instrumented reduction (VSP or TSRH) was performed. 86 patients underwent posterolateral fusion and 82 underwent the same procedure plus a PLIF (done by tightly impacting bone chips into the disc cavity after a very aggressive discectomy). No fusion cages were used. Results: Presented as No-PLIF vs. PLIF. Age: 56 vs. 52 years. Male/Female: 14:72 vs. 15:67. Cases with pars fx: 44% vs. 56%. Level of slip (L3-4, L4-5, L5-S1): 9, 59, 18 vs. 4, 60, 18. Iatrogenic neurological injury: none vs. none. Deep infection: 1 vs. none. Nonunion: 9.3% vs. 2.4%. Broken screws: 6 vs. 2. Degree of slip (pre-op to post-op to 2 years): 34% to 11% to 20% vs. 38% to 4% to 8%. Patients that lost reduction: 67% vs. 18%. Disc height gained at 2 years: −0.2 mm vs. 2.3 mm. Subjective back pain score: 3.5 vs. 2.0. Greenough LBOS score: 54 vs. 62. Patients very satisfied: 43% vs. 60%. Cases with adjacent level slip: 4 vs. 4. Discussion: Spondylolisthesis is commonly treated with a spinal fusion. The goal of surgery is to eliminate motion between the unstable segments, and mechanically it is preferable that the vertebrae fuse in as near anatomic position as possible. It has been shown that the fusion rate decreases with higher degrees of slip, with the spondylolytic types, and with severely degenerated discs. Pedicle screw instrumentation can increase the fusion rate. Reduction of the slip can often be achieved, but it is common to lose the reduction over the course of 1–2 years if only posterolateral fusion is done. Adding an interbody fusion cage can help restore the disc height and widen the intervertebral foramen, but increases complexity, cost, and may actually decrease bone contact area and compression forces. We have found that in grade II and worse slips, pedicle screw fixation alone is not strong enough to maintain reduction of either vertebral alignment or disc height. Adding a chip PLIF appears safe and effective in increasing the union rate and the disc height, and in maintaining reduction in grade II spondylolisthesis. Clinical results are better, the infection rate is not higher. In our hands, there have been no neurological injuries. This study also raises questions about the role and need for interbody fusion cages