Prevalence and Modes of Posterior Hardware Failure With a Staged Protocol for Circumferential Minimally Invasive Surgical Correction of Adult Spinal Deformity: A 13-Year Experience.

BACKGROUND: One of the common complications of adult spinal deformity (ASD) correction is the failure to relieve pain. This may result from the failure of implanted hardware to provide adequate stabilization. While numerous studies exist, characterizing complications that can occur with minimally invasive correction of ASD and data regarding hardware failure in this setting are limited. OBJECTIVE: This article characterizes the rate and mode of posterior hardware failure in the setting of circumferential minimally invasive surgery (CMIS) for ASD correction. METHODS: Patients undergoing staged CMIS correction of ASD from January 2007 to September 2018 were identified. Patients with a minimum 2-year follow-up were included in the study. RESULT: A total of 263 patients (168 women and 95 men) were included in the study. The mean age of patients was 64 years (21-85, SD 13.7), and the mean length of follow-up was 90 months (24-164, SD 40.2). An average of 6 levels (3-16, SD 3.15) was fused per patient.Eight patients had a mechanical hardware failure and required revision surgery (3.04%). No catastrophic failures were noted in our series. Hardware failures were characterized as follows: 2 patients with broken screws, 5 patients with loose screws, and 1 patient who had symptomatic T12-L1 and L5-S1 nonunion with bilateral distal rod fractures, iliac set screw loosening, and proximal T12 screw loosening. Following revision surgery, all of these patients had confirmed solid fusion on computed tomography (CT) scan at their latest follow-up visit.Interestingly, 3 other patients had loosening of the set screw on their iliac bolts. Five patients had rod fractures between L5 and S1 or below S1. All 8 of these patients were asymptomatic with confirmed fusion at L5-S1 on CT scans. CONCLUSION: The prevalence of clinically significant hardware failure needing revision in our series was low at 3.04%. Symptomatic hardware prominence requiring revision was 2.3%. Specifically, rod fractures were not common (2.2%). Our study suggests that in the appropriately selected patient, CMIS to correct ASD without osteotomies may result in acceptable rates of hardware failure. Future studies should compare the results of CMIS deformity correction to a matched population of patients undergoing open deformity correction. CLINICAL RELEVANCE: This study suggests that in the appropriately selected patient, CMIS to correct ASD without osteotomies may result in acceptable rates of hardware failure.

Management of severe adult spinal deformity with circumferential minimally invasive surgical strategies without posterior column osteotomies: a 13-year experience.

OBJECTIVE: To evaluate the mid- to long-term clinical outcomes of circumferential minimally invasive surgery (CMIS) without posterior column osteotomies for severe adult spine deformity (ASD) correction. METHODS: All patients with a minimum of 2-year follow-up undergoing staged CMIS correction of ASD from January 2007 to July 2018 were identified. All included patients had fusion of 3 or more interbody levels that spanned the L5-S1 junction. Only patients with severe deformity, Coronal Cobb > 50° or at least one SRS-Schwab ++ sagittal modifier (SVA > 95 mm, or PI-LL > 20, or PT > 30) were included. All complications were noted. RESULT: 136 patients met inclusion criteria; mean age of patients was 63.6 years (21-85, SD 13.7). The mean follow-up was 82.8 months (24-159, SD 36.6). The mean number of levels fused was 7 (3-16, SD 3). A total of 40 (29.4%) major complications were noted at final follow-ups: 2 (1.4%) intra-operative, 12 (8.9%) peri-operative (≤ 6 weeks from index), 26 (19.1%) post-operative (> 6 weeks from index). There was a total of 53 (40.0%) minor complications. Seven (5.1%) patients who developed radiographic proximal junctional kyphosis. Three patients (2.2%) developed proximal junctional failure. There were 8 (5.9%) cases of pseudarthrosis. Five of these occurred in patients undergoing AxiaLIF. All patients experienced improvements in patient-perceived outcomes (VAS, TIS, ODI, and SRS-22) and radiographic parameters at last follow-up when compared to pre-op (p < 0.05). CONCLUSION: Rates of complications with CMIS correction of severe ASD are lower than published rates of complications seen with open ASD correction. Specifically, the incidence of catastrophic complications is lower. Furthermore, CMIS is associated with significant improvements in clinical and functional outcomes, low rates of pseudarthrosis and proximal junctional kyphosis. Therefore, in the appropriately selected patient, CMIS may be an excellent alternative approach to addressing severe ASD.

Analysis of Spino-Pelvic Parameters and Segmental Lordosis with L5-S1 Oblique Lateral Interbody Fusion at the Bottom of a Long Construct in Circumferential Minimally Invasive Surgical Correction of Adult Spinal Deformity.

BACKGROUND: Lateral interbody fusion (LIF) is an effective adjuvant for circumferential minimally invasive surgery (CMIS) treatment of adult spinal deformity (ASD). Accessing L5-S1 via an oblique LIF (OLIF) approach (OLIF 5-1) allows for anterior LIF (ALIF) at the lumbosacral junction without repositioning the patient. We review the early outcomes and complications of OLIF 5-1 at the bottom of a long construct for an MIS approach to treat ASD. METHODS: We queried a prospectively collected registry of 111 consecutive patients with ASD (Cobb angle >20°, sagittal vertical alignment [SVA] >50, or pelvic incidence [PI]-lumbar lordosis [LL] mismatch>10) patients who underwent CMIS correction between January 2015 and January 2019. Sixty patients had ≥4 levels fused and OLIF 5-1. Multilevel pre-psoas LIF + OLIF 5-1 were performed in the first stage. Three days later, stage 2 involved MIS installation of pedicle screws with aggressive rod contouring and derotation/translation. RESULTS: The mean patient age was 66.8 years (range, 48-79 years), and the mean duration of follow-up was 24 months (range, 3-60 months). A mean of 7 levels were fused (range, 4-9). Significant improvements in L5-S1 segmental lordosis (SL), LL, SVA, PI-LL mismatch, and pelvic tilt were seen following the first stage (P < 0.05). There was no intraoperative vascular, ureteral, or sympathetic chain injury, and no transient or permanent lumbar plexopathy. In 2 patients, OLIF 5-1 was abandoned due to difficult access, and transforaminal LIF was done at L5-S1 at the second stage. Five patients required intraoperative transfusion. No patient experienced postoperative ileus or L5-S1 pseudarthrosis. Significant improvements in visual analog scale pain score, Oswestry Disability Index, 36-Item Short Form Health Survey, and Scoliosis Research Society Outcomes Questionnaire were found. CONCLUSIONS: A single-position MIS OLIF 5-1 at the bottom of a long construct in conjunction with multilevel pre-psoas LIF seems to be a safe and effective technique for improving SL, global LL, and SVA with a low risk of perioperative and postoperative complications.

Biomechanical Analysis of a Novel Buried Fixation Technique Using Headless Compression Screws for the Treatment of Patella Fractures.

The traditional technique for patella fracture fixation utilizes prominent hardware. Prominent hardware use, however, results in a high rate of reoperation for symptomatic implant removal. This biomechanical study evaluates the effectiveness of a novel patella fixation technique that minimizes implant prominence. Patellar transverse osteotomies were created in 13 pairs of cadaveric knees. Paired knees were assigned to either standard fixation (SF) using cannulated partially threaded screws and stainless steel wire tension band, or buried fixation (BF) using headless compression screws with a No. 2 FiberWire tension band and a No. 5 FiberWire cerclage suture. Quadriceps tendons were cyclically loaded to full extension followed by load to failure. The gap across the fracture site, stiffness, and load to failure were measured. The differences in stiffness and load to failure between the 2 groups were not statistically significant. During cyclic loading, significantly greater gapping was observed across the fracture site in the BF group compared with SF group (P < .05). Both constructs failed under loads that exceeded typical loads experienced during the postoperative rehabilitation period. Nevertheless, the BF technique demonstrated larger gap formation and a reduced load to failure than the SF technique. Further clinical studies are therefore underway to determine whether the use of constructs with decreased stability but increased patient comfort could improve clinical outcomes and reduce reoperation rates.

Clinical and Radiologic Fate of the Lumbosacral Junction After Anterior Lumbar Interbody Fusion Versus Axial Lumbar Interbody Fusion at the Bottom of a Long Construct in CMIS Treatment of Adult Spinal Deformity.

INTRODUCTION: Surgeons use numerous arthrodesis strategies for fusion of the lumbosacral junction including anterior lumbar interbody fusion (ALIF) and axial lumbar interbody fusion (AxiaLIF). The optimal L5-S1 fusion strategy remains inconclusive. The purpose of this study is to compare the fate of the lumbosacral junction in ALIF versus AxiaLIF patients in terms of clinical and radiographic outcomes. METHODS: Adult spinal deformity patients, treated with CMIS techniques, with at least 2-year follow-up who underwent AxiaLIF or ALIF at the lumbosacral junction were included. Patients were separated into two groups: AxiaLIF (56 patients) and ALIF (38 patients). Outcome measures included segmental lordosis, sagittal vertical alignment, lumbar lordosis (LL), pelvic incidence-LL mismatch, and pseudarthrosis, major complication, and revision surgery rates. RESULTS: The ALIF group achieved greater postoperative and delta segmental lordosis, higher delta sagittal vertical alignment, higher delta LL, and lower postoperative pelvic incidence-LL mismatch. The pseudarthrosis, major complication, and revision surgery rates were higher in the AxiaLIF group. Five cases of pseudarthrosis at L5-S1 were seen, all in the AxiaLIF group. DISCUSSION AND CONCLUSION: ALIF patients showed more favorable radiographic correction parameters and lower rates of pseudarthrosis, major complications, and revision surgeries. ALIF is the preferred strategy for L5-S1 arthrodesis at a bottom of a long construct.

micro-Opioid receptor stimulation in the medial subnucleus of the tractus solitarius inhibits gastric tone and motility by reducing local GABA activity.

We examined the effects of altering mu-opioid receptor (MOR) activity in the medial subnucleus of the tractus solitarius (mNTS) on several gastric end points including intragastric pressure (IGP), fundus tone, and the receptive relaxation reflex (RRR). Microinjection of the MOR agonist [d-Ala(2),MePhe(4),Gly(ol)(5)]enkephalin (DAMGO; 1-10 fmol) into the mNTS produced dose-dependent decreases in IGP. Microinjection of the endogenous MOR agonists endomorphin-1 and endomorphin-2 (20 fmol) into the mNTS mimicked the effects of 10 fmol DAMGO. Microinjection of 1 and 100 pmol DAMGO into the mNTS produced a triphasic response consisting of an initial decrease, a transient increase, and a persistent decrease in IGP. The increase in IGP appeared to be due to diffusion to the dorsal motor nucleus of the vagus. The effects of 10 fmol DAMGO in the mNTS were blocked by vagotomy and by blockade of MORs, GABA(A) receptors, and ionotropic glutamate receptors in the mNTS. The RRR response was abolished by bilateral microinjection of the opioid receptor antagonist naltrexone into the mNTS and reduced by intravenous administration of naltrexone. Our data demonstrate that 1) activation of MORs in the mNTS with femtomole doses of agonist inhibits gastric motility, 2) the mechanism of MOR effects in the mNTS is through suppression of local GABA activity, and 3) blockade of MORs in the mNTS prevents the RRR response. These data suggest that opioids play an important role in mediating a vagovagal reflex through release of an endogenous opioid in the mNTS, which, in turn, inhibits ongoing local GABA activity and allows vagal sensory input to excite second-order mNTS neurons.

Characterization of noradrenergic transmission at the dorsal motor nucleus of the vagus involved in reflex control of fundus tone.

Quantitative analysis of innervation to dorsal motor nucleus of the vagus (DMV) fundus-projecting neurons indicates that approximately 17% of input neurons are noradrenergic. To determine whether this small percentage of neurons innervating DMV output to the stomach is physiologically relevant, we evaluated the role of norepinephrine at the DMV in mediating a vagovagal reflex controlling the fundus. A strain gauge was sutured onto the fundus of isoflurane-anesthetized rats to monitor changes in tone evoked by esophageal distension (ED). ED produced a decrease in fundus tone of 0.31 +/- 0.02 g (P < 0.05), which could be reproduced after a 30-min interval between distensions. Bilateral cervical vagotomy and/or pretreatment with intravenous atropine methylbromide prevented the reflex-induced fundus relaxation. In contrast, intravenous N(G)-nitro-L-arginine methyl ester had no effect. Bilateral microinjection of alpha2-adrenoreceptor antagonists (yohimbine and RS-79948) into the DMV also prevented the response. Before microinjection of alpha2-adrenoreceptor antagonists, ED decreased fundus tone by 0.33 +/- 0.05 g (P < 0.05). After antagonist microinjection, ED decreased fundus tone by only 0.05 +/- 0.06 g (P > 0.05). Bilateral microinjection of prazosin into the DMV had no effect on the response. Microinjection of norepinephrine into the DMV mimicked the effect of ED and was also prevented by prior microinjection of an alpha2-adrenoreceptor antagonist. Our results indicate that noradrenergic innervation of DMV fundus-projecting neurons is physiologically important and suggest that norepinephrine released at the DMV acts on alpha2-adrenoreceptors to inhibit activity in a cholinergic-cholinergic excitatory pathway to the fundus.