Faculty Bibliography

STUDY DESIGN:: Literature review and meta-analysis. OBJECTIVE:: To compare clinical and radiographic outcomes of patients treated with transarticular screws (TAS) and screw rod constructs (SRC) for posterior atlantoaxial fusion. BACKGROUND:: Modern techniques for C1-2 fusions include Magerl and Seeman's TAS and SRC using C1 lateral mass screws and C2 pars/pedicle screws as described by Goel and Laheri and later modified by Harms and Melcher. METHODS:: Online databases were searched for English-language articles between 1986 and April of 2011 describing posterior atlantoaxial instrumentation with C1-2 TAS or SRC. Forty-five studies (2073 patients) treated with TAS and 24 studies (1073 patients) treated with SRC fulfilled inclusion criteria. Standard and formal meta-analysis techniques were used to compare outcomes. RESULTS:: All studies provided Class III evidence. There were no differences in 30-day mortality (0.8 vs. 0.6%) or neurological injury (0.2 vs. 0%). There was a higher incidence of vertebral artery injury (4.1% [CI: 2.8-5.4%] vs. 2.0% [CI: 1.1-3.4%]; P=0.02) and malpositioned screws (7.1% [CI: 5.7-8.8%] vs. 2.4% [CI: 1.1-4.1%]; P<0.001) and a slightly lower rate of fusion with the TAS technique 97.5% [CI: 95.9-98.5%] vs. 94.6% [CI: 92.6-96.1%]; P<0.001). CONCLUSIONS:: TAS and SRC are safe and effective treatment options for C1-2 instability but require a thorough knowledge of atlantoaxial anatomy for successful insertion of screws. Slightly higher rates of fusion and less risk of injury to the vertebral artery during screw placement were observed with the SRC technique. However, differences in graft material and techniques were noted. Prospective, randomized studies with validated radiographic and clinical outcome metrics are necessary for proper comparison of these techniques.

OBJECTIVE: To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with screw-rod constructs (SRC). METHODS: Online databases were searched for English-language articles published between 1991 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 SRC. There were 24 studies including 1073 patients treated with SRC that fulfilled inclusion criteria. Meta-analysis techniques were used to compare outcomes. RESULTS: All studies provided class III evidence. The 30-day perioperative mortality rate was 0.6%, and neurologic injury occurred in two patients with vertebral artery injury (VAI) from screw malpositions (0.2%). The incidence of clinically significant screw malpositions was 2.4% (confidence interval [CI], 1.1%-4.1%), the incidence of VAI was 2.0% (CI, 1.1%-3.4%), and the rate of fusion with the SRC technique was 97.5% (CI, 95.9%-98.5%). CONCLUSIONS: SRC is a safe and effective treatment option for C1-2 instability. The low but nonzero incidence of screw malposition and VAI emphasizes the necessity of having a thorough knowledge of atlantoaxial anatomy for successful insertion of screws.

OBJECTIVE: Atlantoaxial osteoarthritis (AAOA) is an underrecognized source of neck pain, limitation of range of motion, and cervicogenic headaches. When conservative treatments such as facet injections fail, fusion may be indicated. We reviewed published series describing posterior fusions for atlantoaxial osteoarthritis of the facet joints. METHODS: Online databases were searched for English-language articles describing the diagnosis and treatment of AAOA. Twenty-three studies reporting on 246 patients treated with posterior fusion for lateral AAOA fulfilled inclusion criteria. Standard statistical and formal meta-analytic techniques were used to assess outcomes. RESULTS: All studies provided class III evidence. The 30-day perioperative mortality was 1.2% and neurologic injury did not occur. Patients were followed for a mean of nearly 5 years. Fusion was successful in 98% of patients with a single operation and with 99.5% of patients after revision surgery. Intractable preoperative neck pain either resolved completely or improved in 97.7% of patients. Using meta-analytic techniques, the point estimate for improvement or resolution of pain was 92.6% (confidence interval = 86.8%-96.0%) and the rate of arthrodesis for AAOA was 92.2% (confidence interval = 85.6%-95.9%) and there were no differences among the various techniques used for fusion. Operative complications were few. CONCLUSION: Posterior C1-2 fusion is a safe and effective treatment option for patients with intractable neck pain secondary to lateral AAOA. Modern fusion options offer a high rate of arthrodesis and low risk of morbidity if conservative therapies fail to provide adequate pain relief.

OBJECTIVE: To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with transarticular screw (TAS) fixation. METHODS: Online databases were searched for English-language articles published between 1986 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 TAS fixation. There were 45 studies including 2073 patients treated with TAS that fulfilled inclusion criteria. Meta-analysis techniques were used to calculate outcomes. RESULTS: All studies provided class III evidence. The 30-day perioperative mortality rate was 0.8%, and the incidence of neurologic injury was 0.2%. The incidence of clinically significant malpositioned screws was 7.1% (confidence interval [CI], 5.7%-8.8%), the incidence of vertebral artery injury was 3.1% (CI, 2.3%-4.3%), and the rate of fusion with the TAS technique was 94.6% (CI, 92.6%-96.1%). CONCLUSIONS: TAS fixation is a safe and effective treatment option for C1-2 instability with high rates of fusion (approximately 95%). Screw malposition and vertebral artery injury occurred in approximately 5% of patients. The successful insertion of TAS requires a thorough knowledge of atlantoaxial anatomy.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) promotes the induction of bone growth and is widely used in spine surgery to enhance arthrodesis. Recombinant human BMP-2 has been associated with a variety of complications including ectopic bone formation, adjacent-level fusion, local bone resorption, osteolysis, and radiculitis. Some of the complications associated with rhBMP-2 may be the result of rhBMP-2 induction of the inflammatory host response. In this paper the authors report on a patient with prior transforaminal lumbar interbody fusion (TLIF) using an interbody cage packed with rhBMP-2, in which rhBMP-2 possibly contributed to vascular injury during an attempted anterior lumbar interbody fusion. This 63-year-old man presented with a 1-year history of worsening refractory low-back pain and radiculopathy caused by a Grade 1 spondylolisthesis at L4-5. He underwent an uncomplicated L4-5 TLIF using an rhBMP-2-packed interbody cage. Postoperatively, he experienced marginal improvement of his symptoms. Within the next year and a half the patient returned with unremitting low-back pain and neurogenic claudication that failed to respond to conservative measures. Radiological imaging of the patient revealed screw loosening and pseudarthrosis. He underwent an anterior retroperitoneal approach with a plan for removal of the previous cage, complete discectomy, and placement of a femoral ring. During the retroperitoneal approach the iliac vein was adhered with scarring and fibrosis to the underlying previously operated L4-5 interbody space. During mobilization the left iliac vein was torn, resulting in significant blood loss and cardiac arrest requiring chest compression, defibrillator shocks, and blood transfusion. The patient was stabilized, the operation was terminated, and he was transferred to the intensive care unit. He recovered over the next several days and was discharged at his neurological baseline. The authors propose that the rhBMP-2-induced host inflammatory response partially contributed to vessel fibrosis and scarring, resulting in the life-threatening vascular injury during the reoperation. Spine surgeons should be aware of this potential inflammatory fibrosis in addition to other reported complications related to rhBMP-2.

BACKGROUND: No guidelines exist regarding external cervical orthoses (ECO) after atlantoaxial fusion. We reviewed published series describing C1-2 posterior instrumented fusions with screw-rod constructs (SRC) or transarticular screws (TAS) and compared rates of fusion with and without postoperative ECO. METHODS: Online databases were searched for English-language articles between 1986 and April 2011 describing ECO use after posterior atlantoaxial instrumentation with SRC or TAS. Eighteen studies describing 947 patients who had SRC (+/- ECO: 254 of 693 patients), and 33 studies describing 1424 patients with TAS (+/- ECO: 525 of 899 patients) met inclusion criteria. Meta-analysis techniques were applied to estimate rates of fusion with and without ECO use. RESULTS: All studies provided class III evidence, and no studies directly compared outcomes with or without ECO use. There was no significant difference in the proportion of patients who achieved successful fusion between patients treated with ECO and without ECO for SRC or TAS patients. Point estimates and 95% confidence intervals (CI) for rates of fusion +/- ECO were 97.4% (CI: 95.2% to 98.6%) versus 97.9% (CI: 93.6% to 99.3%) for SRC and 93.6% (CI: 90.7% to 95.6%) versus 95.3% (CI: 90.8% to 97.7%) for TAS. There was no correlation between duration of ECO treatment and fusion (dose effect). CONCLUSIONS: After C1-2 fusion with modern instrumentation, ECO may be unnecessary (class III). Some centers recommend ECO use with patients with softer bone quality (class IV). Prospective, randomized studies with validated radiographic and clinical outcome metrics are necessary to determine the utility of ECO after C1-2 fusion and its impact on patient comfort and cost.

Object Some centers report a lower incidence of vertebral artery (VA) injury with C-2 pars screws compared with pedicle screws without sacrificing construct stability, despite biomechanical studies suggesting greater load failures with C-2 pedicle screws. The authors reviewed published series describing C-2 pars and pedicle screw implantation and atlantoaxial fusions and compared the incidence of VA injury, screw malposition, and successful atlantoaxial fusion with each screw type. Methods Online databases were searched for English-language articles between 1994 and April of 2011 describing the clinical and radiographic outcomes following posterior atlantoaxial fusion with C-1 lateral mass and either C-2 pars interarticularis or pedicle screws. Thirty-three studies describing 2975 C-2 pedicle screws and 11 studies describing 405 C-2 pars screws met inclusion criteria for the safety analysis. Seven studies describing 113 patients treated with C-2 pars screws and 20 studies describing 918 patients treated with C-2 pedicle screws met inclusion criteria for fusion analysis. Standard and formal meta-analysis techniques were used to compare outcomes. Results All studies provided Class III evidence. Ten instances of VA injury occurred with C-2 pedicle screws (0.3%) and no VA injury occurred with pars screws. The point estimate of VA injury for C-2 pedicle screws was 1.09% (95% CI 0.73%-1.63%) and was similar to that of C-2 pars screws (1.48%, 95% CI 0.62%-3.52%). Similarly, there was no statistically significant difference in the rate of clinically significant screw malpositions (1.14% [95% CI 0.77%-1.69%) vs 1.69% [95% CI 0.73%-3.84%]). Radiographically identified screw malposition occurred in a higher proportion of C-2 pedicle screws compared with C-2 pars screws (6.0% [95% CI 3.7%-9.6%] vs 4.0% [95% CI 2.0%-7.6%], p < 0.0001). Pseudarthrosis occurred in a greater proportion of patients treated with C-2 pars screws (5 [4.4%] of 113) compared with those treated with C-2 pedicle screws (2 [0.22%] of 900). Point estimates with 95% confidence intervals show a slightly higher rate of successful atlantoaxial fusion in the pedicle screw cohort (97.8% [CI 96.0%-98.8%] vs 93.5% [CI 86.6%-97.0%]; p < 0.0001). Q-testing ruled out heterogeneity between the study groups. Conclusions With a thorough knowledge of axis anatomy, surgeons can place both C-2 pars and C-2 pedicle screws accurately with a small risk of VA injury or clinically significant malposition. There may be subtle trade-off of safety for rigidity when using axial pedicle instead of pars screws, and the decision to use either screw type must be made only after careful review of the preoperative CT imaging and must take into account the surgeon's expertise and the particular demands of the clinical scenario in any given case.

OBJECTIVE: To review published series describing C1-2 posterolateral instrumentation, comparing outcomes in patients who had and did not have C2 nerve sacrifice. METHODS: Online databases were searched for English-language articles between 1994 and April 2011 pertaining to posterior atlantoaxial instrumentation with C1 lateral mass and C2 screws. Twenty studies describing 732 patients with C2 nerve preservation and 6 studies describing 361 patients with C2 sacrifice met inclusion criteria. RESULTS: All but one small study without a control group were retrospective case series, making all evidence class III. Excluding C2 nerve dysfunction, no neurological deterioration was observed. Three instances of vertebral artery injury were secondary to soft tissue dissection and one was secondary to C1 screw insertion. There were seven instances of C1 screw malposition in the preservation group and none in the section group. Reported in roughly 20% of patients, mean estimated blood loss tended to be lower with C2 nerve sectioning (213 vs. 471 mL) and operative times were somewhat shorter (118 vs. 132 minutes). C2 nerve section resulted in greater symptomatic numbness (11.6% vs. 1.3%; P < 0.0001) but less neuropathic pain (0.3% vs. 4.7%; P = 0.0002) compared with C2 preservation. CONCLUSIONS: Sacrifice of the C2 nerve root to aid in the insertion of C1 lateral mass screws when performing posterior atlantoaxial instrumented fusions is a treatment option (class III). It may decrease blood loss and operative duration, potentially advantageous in elderly or frail patients. Numbness occurred in roughly 12% of patients, an outcome that may be unacceptable to certain patient populations, but neuropathic pain was nearly absent in reported studies with nerve section. C2 nerve preservation and retraction for C1 screw placement may have higher incidence of neuropathic pain (~5%). Rates of fusion are universally high independent of C2 nerve technique.

OBJECTIVE: Iliac crest autograft remains the gold standard for spinal fusion operations. Given risk of donor site morbidity, many centers utilize allograft. We reviewed published series of C1-2 posterolateral instrumented fusions with allograft and autograft. METHODS: Online databases were searched for English-language articles reporting quantifiable outcome data published between 1994 and 2011 of posterior atlantoaxial instrumented arthrodesis with C1 and C2 screws. Thirteen studies describing 652 patients having autograft and seven studies describing 60 patients having allograft serve as the basis of this report. RESULTS: All studies were retrospective case series (Class III evidence). There were no differences in complications or mortality between the groups. There were trends toward shorter operative times and less blood loss using allograft. A higher proportion of patients in the allograft group underwent sacrifice of the C2 nerve root and decortication and packing of the C1-2 joints (P<0.0001). There was no significant difference in the proportion of surviving patients who achieved solid fusion in the autograft (642 of 644 [99.7%]) and allograft patients (59 of 59 [100%]; P = 1.0). CONCLUSIONS: This review is limited by the retrospective data and inconsistent methodology of fusion determination used in most studies. Modern instrumentation and proper surgical techniques result in high rates of successful C1-2 arthrodesis. The use of allograft is a treatment option (Class III evidence) during posterior C1-2 instrumentation and fusion operations. Randomized, controlled trials using standardized radiographic assessments are needed across spinal arthrodesis studies to better determine the prevalence of radiographic fusion and establish technique superiority.

Despite local therapy with curative intent, approximately 30% of men suffer from biochemical relapse. Though some of these PSA relapses are not life threatening, many men eventually progress to metastatic disease and die of prostate cancer. Local therapy is an option for some men, but many have progression of disease following local salvage attempts. One significant issue in this setting is the lack of reliable imaging biomarkers to guide the use of local salvage therapy, as the likely reason for a low cure rate is the presence of undetected micrometastatic disease outside of the prostate/prostate bed. Androgen deprivation therapy is a cornerstone of therapy in the salvage setting. While subsets may benefit in terms of delay in time to metastatic disease and/or death, research is ongoing to improve salvage systemic therapy. Prostate-specific membrane antigen (PSMA) is highly overexpressed by the majority of prostate cancers. While initial methods of exploiting PSMA's high and selective expression were suboptimal, additional work in both imaging and therapeutics is progressing. Salvage therapy and imaging modalities in this setting are briefly reviewed, and the rationale for PSMA-based systemic salvage radioimmunotherapy is described.