William L. Sheppard

Extreme oxatriquinanes and a record C–O bond length

Oxatriquinanes are fused, tricyclic oxonium ions that are known to have exceptional stability compared to simple alkyl oxonium salts. C–O bonds in ethers are generally ∼1.43 Å in length, but oxatriquinane has been found to have C–O bond lengths of 1.54 Å. A search of the Cambridge Structural Database turned up no bona fide C–O bond length exceeding this value. Computational modelling of oxatriquinane alongside other alkyl oxonium ions indicated that the electronic consequences of molecular strain were primarily responsible for the observed bond elongation. We also show that substitution of the oxatriquinane ring system with alkyl groups of increasing steric demand pushes the C–O bond to unheard of distances, culminating in a tert-butyl derivative at a predicted 1.60 Å. Chemical synthesis and an X-ray crystallographic study of these compounds validated the results of the modelling work and, finally, an extraordinary 1.622 Å C–O bond was observed in 1,4,7-tri-tert-butyloxatriquinane. Oxatriquinane is a remarkably stable alkyl oxonium ion, despite the fact that its carbon–oxygen bond lengths are 1.54 Å. The robust nature of this fused tricyclic molecule enabled the addition of increasing steric bulk to the system, culminating in a tri-tert-butyloxatriquinane with a record 1.62 Å C–O bond distance.

Current management of aneurysmal bone cysts

Aneurysmal bone cysts (ABCs) are benign bone lesions arising predominantly in the pediatric population that can cause local pain, swelling, and pathologic fracture. Primary lesions, which constitute roughly two thirds of all ABCs, are thought to be neoplastic in nature, with one third of ABCs arising secondary to other tumors. Diagnosis is made with various imaging modalities, which exhibit characteristic features such as “fluid-fluid levels,” although biopsy is critical, as telangiectatic osteosarcoma cannot be excluded based on imaging alone. Currently, the standard of care and most widely employed treatment is intralesional curettage. However, tumor recurrence with curettage alone is common and has driven some to propose a multitude of adjuvants with varying efficacy and risk profiles. Historically, therapies such as en bloc resection or radiation therapy were utilized as an alternative to decrease the recurrence rate, but these therapies imposed high morbidity. As a result, modern techniques now seek to simultaneously reduce morbidity and recurrence, the pursuit of which has produced preliminary study into minimally invasive percutaneous treatments and medical management.

Extreme Oxatriquinanes: Structural Characterization of α-Oxyoxonium Species with Extraordinarily Long Carbon–Oxygen Bonds

The first stable α-oxyoxonium species have been synthesized and characterized. Strong donation of nonbonding electrons on oxygen into the adjacent σ*(C-O(+)) orbital was predicted by modeling to result in unheard of carbon-oxygen bond lengths. The kinetic stability of the triquinane ring system provides a platform upon which to study these otherwise elusive species, which are evocative of intermediates on the acetalization reaction pathway. Crystallographic analysis of the α-hydroxy and α-methoxy oxatriquinane triflates reveals 1.658 and 1.619 Å C-O(+) bond lengths, respectively, the former of which is a new record for the C-O bond.

Articular Cartilage Lesion Characteristic Reporting Is Highly Variable in Clinical Outcomes Studies of the Knee

Objective The purpose of this study was to investigate the degree of standardized evaluation and reporting of cartilage lesion characteristics in high-impact clinical studies for symptomatic lesions of the knee. We hypothesized that there are significant inconsistencies in reporting these metrics across orthopedic literature. Design A total of 113 clinical studies on articular cartilage restoration of the knee were identified from 6 high-impact orthopedic journals between 2011 and 2016. Full-text review was used to evaluate sources for details on study methodology and reporting on the following variables: primary procedure, location, size, grade, and morphology of cartilage lesions. Results All studies reported on the type of primary cartilage procedure and precise lesion location(s). Approximately 99.1% reported lesion morphology (chondral, osteochondral, mixed). For lesion size, 32.7% of articles did not report how size was measured and 11.5% did not report units. The lesion sizing method was variable, as 27.4% used preoperative magnetic resonance imaging to measure/report lesion size, 31.0% used arthroscopy, and 8.8% used both. The majority of studies (83.2%) used area to report size, and 5.3% used diameter. Formal grading was not reported in 17.7% of studies. Only 54.8% of studies reported depth when sizing osteochondral defects. Conclusions Recent literature on cartilage restoration provides adequate information on surgical technique, lesion location, and morphology. However, there is wide variation and incomplete reporting on lesion size, depth, and grading. Future clinical studies should include these important data in a consistent manner to facilitate comparison among surgical techniques.

Regression of Disc-Osteophyte Complexes Following Laminoplasty Versus Laminectomy with Fusion for Cervical Spondylotic Myelopathy

Background Laminectomy with fusion (LF) and laminoplasty are two posterior-based surgical approaches for the surgical treatment of cervical spondylotic myelopathy (CSM). The decompressive effect of these approaches is thought to be primarily related to the dorsal drift of the spinal cord away from ventral compressive structures. A lesser known mechanism of spinal cord decompression following cervical LF is regression of the ventral disc osteophyte complexes which is postulated to result from the alteration of motion across the fused motion segment. The goal of this study was to determine whether regression of the ventral disc-osteophyte complexes occur following laminoplasty and compare the magnitude of this occurrence to cervical laminectomy and fusion. Methods Seventy patients with CSM who underwent pre- and postoperative magnetic resonance imaging (MRI) and were treated with either laminoplasty or LF. The size of the disc-osteophyte complex at all operative levels were measured on pre- and postoperative MRI using digital calipers. Results The laminoplasty group consisted of 25 patients with an average age of 54.9 and a mean of 3.24 surgical levels while the LF group consisted of 45 patients with an average age of 65.4 and a mean of 3.44 surgical levels (age, p < 0.0001; levels, p= 0.46). The average time interval between pre- and post-operative MRI was 16.2 and 15.6 months in the laminoplasty and LF groups, respectively (p = 0.91). The average time interval between surgery and post-operative MRI was 10.1 and 10.7 months in the laminoplasty and LF groups, respectively (p = 0.86). When comparing pre- and post-operative MRI, there was a 9.59% decrease in disc-osteophyte complex size from 3.84mm ± 0.74 to 3.47mm ± 0.86 in the laminoplasty group compared to a 35.4% decrease in disc-osteophyte complex size from 4.60mm ± 1.06 to 2.98mm ± 1.33 in LF group (laminoplasty, p < 0.0001; LF, p = 0.0067). Using logistic regression analysis, LF, increased time interval between surgery and post-operative MRI, high cobb angle, and straight sagittal alignment were all independently associated with increased disc-osteophyte complex regression (p < 0.05). No differences in functional outcomes (as defined by mJOA scores) was found between the two surgical techniques. Conclusions In patients with CSM that had a posterior surgical approach, LF is associated with a larger interval regression in disc-osteophyte complex size compared to laminoplasty. This is likely related to the loss of motion of the cervical spine after surgery as governed by Wolff’s law and the Heuter-Volkmann’s principle. Although the decompressive effect of LF and laminoplasty is primarily related to the dorsal drift of the spinal cord away from ventral compressive structures, disc-osteophyte complex regression likely provides another mechanism of spinal cord decompression.

Use of the subcutaneous lumbar spine (SLS) index as a predictor for surgical complications in lumbar spine surgery

BACKGROUND CONTEXT Lumbar spine surgeries require adequate exposure to visualize key structures and limited exposure can make surgery more technically difficult, thus increasing the potential for complications. Body mass index and body mass distribution have been shown to be associated with worse surgical outcomes. PURPOSE This study aims to further previous investigations in elucidating the predictive nature of body mass distribution with peri- and postoperative complications in lumbar surgery. STUDY DESIGN/SETTING This is a retrospective study conducted at a single institution. PATIENT SAMPLE Two hundred eighty-five patients who underwent lumbar laminectomy, laminotomy, or posterior lumbar interbody fusion or transforaminal lumbar interbody fusion procedures between 2013 and 2016. OUTCOME MEASURES Magnetic resonance imaging (MRI) results and electronic medical records were reviewed for measurements and relevant complications. METHODS Previously known risk factors were identified and MRI measurements of subcutaneous adipose depth (SAD) relative to spinous process height (SPH) were measured at the surgical site to generate the subcutaneous lumbar spine (SLS) index. This measurement was then analyzed in association with recorded surgical complications. RESULTS The SLS index was found to be a significant risk factor for total complications (0.292, p=.041), perioperative complications (0.202, p=.015), and need for revision surgery (0.285, p<.001). The SAD alone proved to be negatively associated with perioperative complications (-0.075, p=.034) and need for revision surgery (-0.104, p=.001), with no predictive association seen for total or postoperative complications. Linear regression revealed an SLS index of 3.43 as a threshold value associated with a higher risk of total complications, 5.8 for perioperative complications, and 3.81 for the need for revision surgeries. CONCLUSION Body mass distribution of the surgical site as indicated by SAD to SPH (SLS index) is significantly associated with increasing risk of postoperative and perioperative complications as well as increased likelihood for necessary revision surgery. This relationship was shown to be a more accurate indication of perioperative risk than previous standards of body mass index and SAD alone, and may allow spine surgeons to assess surgical risk when considering lumbar spine surgery using simple calculations from standard preoperative MRI results.

The combined administration of vancomycin IV, standard prophylactic antibiotics, and vancomycin powder in spinal instrumentation surgery: does the routine use affect infection rates and bacterial resistance?

Background Surgical site infections (SSI) poses significant risk following spinal instrumentation surgery. The 2013 North American Spine Society (NASS) Evidence-Based Clinical Guidelines found that the incidence of SSI in spine surgery ranged from 0.7-10%, with higher rates with medical comorbidities. National guidelines currently recommend first-generation cephalosporins as first line prophylaxis. Due to an increase in MRSA cases in our institution, a combined antibiotic strategy using vancomycin IV, standard prophylactic antibiotics, and vancomycin powder was implemented for all spinal instrumentation surgeries. Methods All spinal instrumentation surgeries performed at this institution from 2013-2016 were identified. Chart review was then performed to identify the inclusion and exclusion criteria, demographic data, diagnosis, type of surgery performed, and bacterial culture results. Rates of SSI, as defined by the Center for Disease Control (CDC), were calculated and antibiotic resistance was determined. As control, SSIs were identified and reviewed from 2010, prior to the implementation of the combined strategy. Results One thousand and seventy four subjects were identified in the combined cohort. Mean age was 52.3 years, 540 males (50.2%), 534 females (49.8%). There were 960 primary surgeries (89.4%), 114 cases revision surgeries (10.6%). Cervical myelopathy (27.9%), lumbar stenosis (16.2%), lumbar spondylolisthesis (14.0%), and scoliosis (pediatric and adult)/deformity (13.7%) were leading diagnoses. The standard prophylactic antibiotic was cefazolin IV in 524 cases (48.8%), gentamicin IV in 526 cases (49.0%), vancomycin powder was used in 72.3% of cases. Four SSI cases out of 1,074 were identified (0.37%), 3 deep and 1 superficial, with no antibiotic resistance. In the control group, there were 11 infections of 892 cases (1.23%). There were significantly lower rates of SSI in the combined group versus control (P=0.05). Conclusions The combined antibiotic strategy led to low SSI rates in this retrospective case control study. Limitations of this study include retrospective design and small sample size. A large multicenter randomized clinical trial may provide further insight in the effectiveness of this strategy. Level of evidence 3. Clinical relevance: the combined antibiotic protocol may be considered in institutions with concern for SSI and methicillin resistant infections associated with spinal instrumentation surgeries.

Utility of Intraoperative Neuromonitoring for Lumbar Pedicle Screw Placement Is Questionable: A Review of 9957 Cases

Study Design. A retrospective database study. Objective. The goal of this study was to (1) evaluate the trends in the use of electromyography (EMG) for instrumented posterolateral lumbar fusions (PLFs) in the United States and (2) assess the risk of neurological injury following PLFs with and without EMG. Summary of Background Data. Neurologic injuries from iatrogenic pedicle wall breaches during screw placement are known complications of PLFs. The routine use of intraoperative neuromonitoring (ION) such as EMG during PLF to improve the accuracy and safety of pedicle screw implantation remains controversial. Methods. A retrospective review was performed using the PearlDiver Database to identify patients who had PLF surgery with and without EMG for lumbar disorders from years 2007 to 2015. Patients undergoing concomitant interbody fusions or spinal deformity surgery were excluded. Demographic trends and risk of neurological injuries were assessed. Results. During the study period, 2007 to 2015, 9957 patients underwent PLFs. Overall, EMG was used in 2495 (25.1%) of these patients. There was a steady increase in the use of EMG from 14.9% in 2007 to 28.7% in 2009, followed by a steady decrease to 21.9% in 2015 (P < 0.0001). The risk of postoperative neurological injuries following PLFs was 1.35% (134/9957) with a risk of 1.36% (34/2495) with EMG and 1.34% (100/7462) without EMG (P = 0.932). EMG is used most commonly for PLFs in the Southern part of the United States. Conclusion. In this retrospective national database review, we found that there was a steady increase in the routine use of EMG for PLFs followed by a steady decline. Regional differences were observed in the utility of EMG for PLFs. The risk of neurological complications following PLF in the absence of spinal deformity is low and the routine use of EMG for PLF may not decrease the risk. Level of Evidence: 4

Staged Reconstruction of Diaphyseal Fractures with Segmental Defects: Surgical and Patient-Reported Outcomes

INTRODUCTION Two-stage limb reconstruction is an option for patients with critical size segmental bone defects following acute trauma or non-union. Reconstruction is technically demanding and associated with a high complication rate. Current protocols for limb reconstruction have well-documented challenges, and no study has reported on patient outcomes using a validated questionnaire. In this study, we aimed to examine the clinical and patient-centered outcomes following our surgical protocol for two-stage limb reconstruction following critical size segmental defects. PATIENTS AND METHODS A single surgeon performed reconstruction of long bone defects using antibiotic impregnated cement spacers and intramedullary cancellous bone autograft. A retrospective chart review was performed. Three reviewers independently measured time to union based on radiographs. The Lower Extremity Functional Scale (LEFS) survey was administered to patients after most recent follow-up. RESULTS Ten limbs representing nine patients were included. All patients sustained a lower extremity injury, and one patient had bilateral lower extremity injuries. Average clinical follow-up was 18.3 months (range 7-33) from final surgical intervention, and follow-up to questionnaire administration was 28 months (range 24-37). The mean time between stages was 3.1 months. Average time to unrestricted weight-bearing was 7.9 months from Stage 1 (range 3.4-15.9) and 4.5 months from Stage 2 (range 1.1-11.6). Average time to full union was 16.7 months from Stage 1 (range 6.4-28.6) and 13.5 months from Stage 2 (range 1.8-27). Eight patients (nine limbs) participated in the LEFS survey, the average score was 53.1 (range 30-67), equating to 66% of full functionality (range 38%-84%). Complications included 5 infections, 3 non-unions, and one amputation. There was a moderate positive correlation between infection at any time point and non-union (R=0.65, p=0.03). DISCUSSION AND CONCLUSIONS Outcomes in this small patient cohort were good despite risks of complication. There is an association between infection and non-union. Further studies addressing clinical and functional outcomes will help to guide expectations for future surgeons and patients.