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Chlorhexidine skin antisepsis is frequently recommended for most surgical procedures; however, it is unclear if these recommendations should apply to surgery involving traumatic contaminated wounds where povidone-iodine has previously been preferred. We aimed to compare the effect of aqueous 10% povidone-iodine versus aqueous 4% chlorhexidine gluconate on the risk of surgical site infection in patients who required surgery for an open fracture.We conducted a multiple-period, cluster-randomised, crossover trial (Aqueous-PREP) at 14 hospitals in Canada, Spain, and the USA. Eligible patients were adults aged 18 years or older with an open extremity fracture treated with a surgical fixation implant. For inclusion, the open fracture required formal surgical debridement within 72 h of the injury. Participating sites were randomly assigned (1:1) to use either aqueous 10% povidone-iodine or aqueous 4% chlorhexidine gluconate immediately before surgical incision; sites then alternated between the study interventions every 2 months. Participants, health-care providers, and study personnel were aware of the treatment assignment due to the colour of the solutions. The outcome adjudicators and data analysts were masked to treatment allocation. The primary outcome was surgical site infection, guided by the 2017 US Centers for Disease Control and Prevention National Healthcare Safety Network reporting criteria, which included superficial incisional infection within 30 days or deep incisional or organ space infection within 90 days of surgery. The primary analyses followed the intention-to-treat principle and included all participants in the groups to which they were randomly assigned. This study is registered with ClinicalTrials.gov, NCT03385304.Between April 8, 2018, and June 8, 2021, 3619 patients were assessed for eligibility and 1683 were enrolled and randomly assigned to povidone-iodine (n=847) or chlorhexidine gluconate (n=836). The trial's adjudication committee determined that 45 participants were ineligible, leaving 1638 participants in the primary analysis, with 828 in the povidone-iodine group and 810 in the chlorhexidine gluconate group (mean age 44·9 years [SD 18·0]; 629 [38%] were female and 1009 [62%] were male). Among 1571 participants in whom the primary outcome was known, a surgical site infection occurred in 59 (7%) of 787 participants in the povidone-iodine group and 58 (7%) of 784 in the chlorhexidine gluconate group (odds ratio 1·11, 95% CI 0·74 to 1·65; p=0·61; risk difference 0·6%, 95% CI -1·4 to 3·4).For patients who require surgical fixation of an open fracture, either aqueous 10% povidone-iodine or aqueous 4% chlorhexidine gluconate can be selected for skin antisepsis on the basis of solution availability, patient contraindications, or product cost. These findings might also have implications for antisepsis of other traumatic wounds.US Department of Defense, Canadian Institutes of Health Research, McMaster University Surgical Associates, PSI Foundation.

Author(s): Pogorzelski, David; Nguyen, Uyen; McKay, Paula; Thabane, Lehana; Camara, Megan; Ramsey, Lolita; Seymour, Rachel; Goodman, J Brett; McGee, Sheketha; Fraifogl, Joanne; Hudgins, Andrea; Tanner, Stephanie L; Bhandari, Mohit; Slobogean, Gerard P; Sprague, Sheila; PREP-IT Investigators Executive Committee:; Steering Committee; Adjudication Committee; Data and Safety Monitoring Committee; Research Methodology Core; Patient Centred Outcomes Core; Orthopaedic Surgery Core; Operating Room Core; Infectious Disease Core; Military Core; McMaster University Methods Center; University of Maryland School of Medicine Administrative Center; University of Maryland School of Pharmacy, The PATIENTS Program; PREP-IT Clinical Sites: Lead Clinical Site (Aqueous-PREP and PREPARE); Aqueous-PREP and PREPARE; Aqueous-PREP; PREPARE; PREP-IT Investigators Executive Committee | Abstract: IntroductionPragmatic trials in comparative effectiveness research assess the effects of different treatment, therapeutic, or healthcare options in clinical practice. They are characterized by broad eligibility criteria and large sample sizes, which can lead to an unmanageable number of participants, increasing the risk of bias and affecting the integrity of the trial. We describe the development of a sampling strategy tool and its use in the PREPARE trial to circumvent the challenge of unmanageable work flow.MethodsGiven the broad eligibility criteria and high fracture volume at participating clinical sites in the PREPARE trial, a pragmatic sampling strategy was needed. Using data from PREPARE, descriptive statistics were used to describe the use of the sampling strategy across clinical sites. A Chi-square test was performed to explore whether use of the sampling strategy was associated with a reduction in the number of missed eligible patients.Results7 of 20 clinical sites (35%) elected to adopt a sampling strategy. There were 1539 patients excluded due to the use of the sampling strategy, which represents 30% of all excluded patients and 20% of all patients screened for participation. Use of the sampling strategy was associated with lower odds of missed eligible patients (297/4545 (6.5%) versus 341/3200 (10.7%) p l 0.001).ConclusionsImplementing a sampling strategy in the PREPARE trial has helped to limit the number of missed eligible patients. This sampling strategy represents a simple, easy to use tool for managing work flow at clinical sites and maintaining the integrity of a large trial.

OBJECT The authors present clinical outcome data and satisfaction of patients who underwent minimally invasive vertebral body corpectomy and cage placement via a mini-open, extreme lateral, transpsoas approach and posterior short-segment instrumentation for lumbar burst fractures. METHODS Patients with unstable lumbar burst fractures who underwent corpectomy and anterior column reconstruction via a mini-open, extreme lateral, transpsoas approach with short-segment posterior fixation were reviewed retrospectively. Demographic information, operative parameters, perioperative radiographic measurements, and complications were analyzed. Patient-reported outcome instruments (Oswestry Disability Index [ODI], 12-Item Short Form Health Survey [SF-12]) and an anterior scar-specific patient satisfaction questionnaire were recorded at the latest follow-up. RESULTS Twelve patients (7 men, 5 women, average age 42 years, range 22–68 years) met the inclusion criteria. Lumbar corpectomies with anterior column support were performed (L-1, n = 8; L-2, n = 2; L-3, n = 2) and supplemented with short-segment posterior instrumentation (4 open, 8 percutaneous). Four patients had preoperative neurological deficits, all of which improved after surgery. No new neurological complications were noted. The anterior incision on average was 6.4 cm (range 5–8 cm) in length, caused mild pain and disability, and was aesthetically acceptable to the large majority of patients. Three patients required chest tube placement for pleural violation, and 1 patient required reoperation for cage subsidence/hardware failure. Average clinical follow-up was 38 months (range 16–68 months), and average radiographic follow-up was 37 months (range 6–68 months). Preoperative lumbar lordosis and focal lordosis were significantly improved/maintained after surgery. Patients were satisfied with their outcomes, had minimal/moderate disability (average ODI score 20, range 0–52), and had good physical (SF-12 physical component score 41.7% ± 10.4%) and mental health outcomes (SF-12 mental component score 50.2% ± 11.6%) after surgery. CONCLUSIONS Anterior corpectomy and cage placement via a mini-open, extreme lateral, transpsoas approach supplemented by short-segment posterior instrumentation is a safe, effective alternative to conventional approaches in the treatment of single-level unstable burst fractures and is associated with excellent functional outcomes and patient satisfaction.

Background context Cervical spine clearance protocols were developed to standardize the clearance of the cervical spine after blunt trauma and prevent secondary neurologic injuries. The degree of incorporation of evidence-based guidelines into protocols at trauma centers in California is unknown. Purpose To evaluate the cervical spine clearance protocols in all trauma centers of California. Study design An observational cross-sectional study. Patient sample Included from Level I, II, III trauma centers in California. Outcome measures The self-reported outcomes of each trauma center's cervical spine clearance protocols were assessed. Methods Level I (n=15), II (n=30), and III (n=11) trauma centers in California were contacted. Each available protocol was reviewed for four scenarios: clearing the asymptomatic patient, the initial imaging modality used in patients not amenable to clinical clearance, and the management strategies for patients with persistent neck pain with a negative computed tomography (CT) scan and those who are obtunded. Results were compared with the 2009 Eastern Association for the Surgery of Trauma (EAST) cervical spine clearance guidelines. Results The response rate was 96%. Sixty-three percent of California's trauma centers (Level I, 93%; Level II, 60%; Level III, 27%) had written cervical spine clearance protocols. For asymptomatic patients, 83% of Level I and 61% of Level II centers used National Emergency X-Radiography Utilization Study criteria with/without painless range of motion. For those requiring imaging, 67% of Level I and 56% of Level II centers stated a CT scan should be the first line of imaging. For obtunded patients and patients with persistent neck pain and a negative CT scan, more than 90% of Level I and more than 70% of Level II trauma centers incorporated the 2009 EAST recommendations. No institution recommended passive flexion-extension radiographs for the obtunded patient. Conclusions Written cervical spine clearance protocols exist in 63% of California's trauma centers and only 51% of the centers have protocols that follow current evidence-based guidelines. Standardization and utilization of these protocols should be encouraged to prevent missed injuries and secondary neurologic injuries.

Introduction Studies document rod fracture in pedicle subtraction osteotomy (PSO) settings where disk spaces were preserved above or adjacent to the PSO. This study compares the multidirectional bending rigidity and fatigue life of PSO segments with or without interbody support. Methods Twelve specimens received bilateral T12–S1 posterior fixation and L3 PSO. Six received extreme lateral interbody fusion (XLIF) cages in addition to PSO at L2–L3 and L3–L4; six had PSO only. Flexion-extension, lateral bending, and axial rotation (AR) tests were conducted up to 7.5 Newton-meters (Nm) for groups: (1) posterior fixation, (2) L3 PSO, (3) addition of cages (six specimens). Relative motion across the osteotomy (L2–L4) and entire fixation site (T12–S1) was measured. All specimens were then fatigue tested for 35K cycles. Results Regardingmultiaxial bending, there was a significant 25.7% reduction in AR range of motion across L2–L4 following addition of cages. Regarding fatigue bending, dynamic stiffness, though not significant ( p = 0.095), was 22.2% greater in the PSO + XLIF group than in the PSO-only group. Conclusions Results suggest that placement of interbody cages in PSO settings has a potential stabilizing effect, which is modestly evident in the acute setting. Inserting cages in a second-stage surgery remains a viable option and may benefit patients in terms of recovery but additional clinical studies are necessary to confirm this.

Object Expandable cages are becoming more popular due in large part to their versatility, but subsidence and catastrophic failure remain a concern. One of the proposed reasons of failure is edge loading of the endplate caused by a mismatch between the sagittal alignment of the motion segment and cage. This in vitro analysis investigates the endplate forces characteristic of expandable and fixed interbody cages in a single-level human cadaver corpectomy model. Methods Ten human thoracolumbar spines (T10–L2, L3–5) were biomechanically evaluated following a single-level corpectomy that was reconstructed with an expandable or fixed cage. Fixed cages were deployed with the best-fitting end cap combination, whereas expandable cages were deployed in normal, hypolordotic, and hyperlordotic alignment scenarios. The endplate forces and contact area were measured with a pressure measurement system, and the expansion torque applied by the surgeon was measured with a custom-made insertion device. Results The contact areas of the expandable cages were, in general, higher than those of the fixed cages. The endplate forces of the expandable cages were similar to those of the fixed cages in the normal alignment scenario. Higher endplate forces were observed in the hyperlordotic scenario, whereas the endplate forces in the hypolordotic and normal alignment scenarios were similar. There was no correlation with the expansion torque and the final endplate forces. Conclusions Expandable cages resulted in consistently higher contact area and endplate forces when compared with the fixed cages. Because the expansion torque does not correlate with the final endplate forces, surgeons should not rely solely on tactile feedback during deployment of these cages.

Object Ankylosing spondylitis (AS) is a genetic condition that frequently results in spinal sagittal plane deformity of thoracolumbar or cervicothoracic junctions. Generally, a combination of osteotomy and spinal fixation is used to treat severe cases. Although surgical techniques for traumatic injury across the cervicothoracic junction have been well characterized in clinical and biomechanical literature, the specific model of instrumented opening wedge osteotomy in autofused AS has not been studied biomechanically. This study characterizes the structural stability of various posterior fixation techniques across the cervicothoracic junction in spines with AS, specifically considering the effects of posterior rod diameter and material type. Methods For each of 10 fresh-frozen human spines (3 male, 7 female; mean age 60 ± 10 years; C3–T6), an opening wedge osteotomy was performed at C7–T1. Lateral mass screws were inserted bilaterally from C-4 to C-6 and pedicle screws from T-1 to T-3. For each specimen, 3.2-mm titanium (Ti), 3.5-mm Ti, and 3.5-mm cobalt chromium (CoCr) posterior spinal fusion rods were tested. To simulate the anterior autofusion and long lever arms characteristic of AS, anterior cervical plates were placed from C-4 to C-7 and T-1 to T-3 using fixed angle screws. Nondestructive flexion-extension, lateral bending, and axial rotation tests were conducted to 3.0 Nm in each anatomical direction; 3D motion tracking was used to monitor primary range of motion across the osteotomy (C7–T1). Biomechanical tests used a repeat-measures test design. The order of testing for each rod type was randomized across specimens. Results Constructs instrumented with 3.5-mm Ti and 3.5-mm CoCr rods were significantly stiffer in flexion-extension than those with the 3.2-mm Ti rod (25.2% ± 16.4% and 48.1% ± 15.3% greater than 3.2-mm Ti, respectively, p < 0.05). For axial rotation, the 3.5-mm Ti and 3.5-mm CoCr constructs also exhibited a significant increase in rigidity compared with the 3.2-mm Ti construct (36.1% ± 12.2% and 52.0% ± 20.0%, respectively, p < 0.05). There were no significant differences in rigidity seen between the 3 types of rods in lateral bending (p > 0.05). The 3.5-mm CoCr rod constructs showed significantly higher rigidity in flexion-extension than the 3.5-mm Ti rod constructs (33.1% ± 15.5%, p < 0.05). There was a trend for 3.5-mm CoCr to have greater rigidity in axial rotation (36.2% ± 18.6%), but this difference was not statistically significant (p > 0.05). Conclusions The results of this study suggest that 3.5-mm CoCr rods are optimal for achieving the most rigid construct in opening wedge osteotomy in the cervicothoracic region of an AS model. Rod diameter and material properties should be considered in construct strategy. Some surgeons have advocated anterior plating in patients with AS after osteotomy for additional stability and bone graft surface. Although this effect was not examined in this study, additional posterior stability achieved with CoCr may decrease the need for additional anterior procedures.

Object Primary spine tumors frequently involve the C-2 vertebra. Complete resection of the lesion may require total removal of the C-2 vertebral body, pedicles, and dens process. Authors of this biomechanical study are the first to evaluate a comprehensive set of reconstruction methods after C-2 resection to determine the optimal configuration depending on the degree of excision required. Methods Eight human heads (from the skull to C-6) from 4 males and 4 females with a mean age of 68 ± 18 years at death were cleaned of tissue, while leaving ligaments and discs intact. Nondestructive flexion and extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted using a nonconstraining, pure moment loading apparatus, and relative motion across the fusion site (C1–3) was measured using a 3D motion tracking system. Specimens were tested up to 1.5 Nm at 0.25-Nm intervals for 45 seconds each. The spines were instrumented using 3.5-mm titanium rods with a midline occipitocervical plate (4.0 × 12–mm screws) and lateral mass screws (excluding C-2) at the C-1 (3.0 × 40 mm) and C3–5 levels (3.0 × 16 mm). Testing was repeated for the following configurations: Configuration 1 (CF1), instrumentation only from occiput to C-5; CF2, C-2 corpectomy leaving the dens; CF3, titanium mesh cage (16-mm diameter) from C-3 to C-1 ring and dens; CF4, removal of cage, C-1 ring, and dens; CF5, titanium mesh cage from C-3 to clivus (16-mm diameter); CF6, removal of C-2 posterior elements leaving the C3–clivus cage (spondylectomy); CF7, titanium mesh cage from C-3 to clivus (16-mm diameter) with 2 titanium mesh cages from C-3 to C-1 lateral masses (12-mm diameter); and CF8, removal of all 3 cages. A crosslink was added connecting the posterior rods for CF1, CF6, and CF8. Range-of-motion (ROM) differences between all groups were compared via repeated-measures ANOVA with paired comparisons using the Student t-test with a Tukey post hoc adjustment. A p < 0.05 indicated significance. Results The addition of a central cage significantly increased FE rigidity compared with posterior instrumentation alone but had less of an effect in AR and LB. The addition of lateral cages did not significantly improve rigidity in any bending direction (CF6 vs CF7, p > 0.05). With posterior instrumentation alone (CF1 and CF2), C-2 corpectomy reduced bending rigidity in only the FE direction (p < 0.05). The removal of C-2 posterior elements in the presence of a C3–clivus cage did not affect the ROM in any bending mode (CF5 vs CF6, p > 0.05). A crosslink addition in CF1, CF6, and CF8 did not significantly affect primary or off-axis ROM (p > 0.05). Conclusions Study results indicated that posterior instrumentation alone with 3.5-mm rods is insufficient for stability restoration after a C-2 corpectomy. Either C3–1 or C3–clivus cages can correct instability introduced by C-2 removal in the presence of posterior instrumentation. The addition of lateral cages to a C3–clivus fusion construct may be unnecessary since it does not significantly improve rigidity in any direction.

Biomechanical.Evaluate spinal stability achieved with different levels of posterior percutaneous fixation (postPerc) for thoracolumbar fractures in cadavers subjected to ICU activities."Spine damage control" involves postPerc performed within 24 hours of injury and staged, elective, definitive stabilization. Amount of instrumentation needed to initially achieve adequate spinal stability, minimize morbidity, and accommodate ICU care needs between stages are not defined.In full-unembalmed cadavers motion-tracking sensors were placed at T11 and L1. A T12 corpectomy with PLC injury was stabilized with 1, 2, and 3 levels of PostPerc above/below the injury. Motions between T11 and L1 were measured during Log-Roll and Sit-Up on an ICU bed. After in situ testing, anatomic spinal motion ranges were determined under pure moment loads.5 cadavers were evaluated. For Log-Roll, 2 and 3 levels above/below restored stability to intact, whereas 1 level above/below did not for axial rotation. For translation, all instrumentation restored stability to intact. During Sit-Up, a linear increase in flexion was observed. At 45° Sit-Up, 2 and 3 levels above/below were similar to intact for flexion; 1 level above/below had significantly more flexion. All instrumentations restored translation to intact for Sit-Up; significantly more axial collapse occurred for instrumentation compared with intact. During ex situ testing, 2 and 3 levels above/below were similar; 1 level above/below had significantly greater laxity in flexion, extension, and axial rotation.Posterior instrumentation 2 or 3 levels above/below a severe thoracolumbar fracture model can restore spinal stability back to its intact condition. 2 levels of fixation above/below this "worst-case scenario" is minimum fixation sufficient to provide absolute spinal stability in the ICU setting as a "Damage Control" technique in patients with polytrauma. In less severe injury models, 1 level of fixation above/below may provide adequate spinal stability; although this should be confirmed in future investigations.N/A.

Preoperative assessment of bone mineral density (BMD) via dual X-ray absorptiometry (DEXA) has been shown to help determine the need for screw augmentation, particularly in the pedicle. However, patients frequently present without preoperative DEXA scans, especially in trauma situations. We developed a “smart” probe for intra-operative assessment of local bone strength in the pedicle. A standard ball tip probe was instrumented with an in-line load cell and was used to test the bone strength of fresh-frozen human cadaveric lumbar spine. Local bone crush strength was assessed using the probe at five locations within the centrum and the pedicle. The contralateral pedicle was outfitted with a standard pedicle screw and insertion torque and pull-out force of the screw were measured. Correlation was found between PS-centrum (probe strength-centrum) and screw pull-out strength (adj. R2 = 0.42). A stepwise linear regression revealed that when considering BMD, insertion torque, and PS-centrum, pull-out strength could be predicted based on PS-centrum and insertion torque (adj. R2 = 0.51, p

Background Since the introduction of rhBMP-2 (Infuse®) in 2002, surgeons have had an alternative substitute to autograft and its related donor site morbidity. Recently, the prevalence of reported adverse events and complications related to the use of rhBMP-2 has raised many ethical and legal concerns for surgeons. Additionally, the cost and decreasing reimbursement landscape of rhBMP-2 use have required identification of a viable alternative. Osteo allogeneic morphogenetic protein (OsteoAMP®) is a commercially available allograft-derived growth factor rich in osteoinductive, angiogenic, and mitogenic proteins. This study compares the radiographic fusion outcomes between rhBMP-2 and OsteoAMP allogeneic morphogenetic protein in lumbar interbody fusion spine procedures. Methods Three hundred twenty-one (321) patients from three centers underwent a transforaminal lumbar interbody fusion (TLIF) or lateral lumbar interbody fusion (LLIF) procedure and were assessed by an independent radiologist for fusion and radiographically evident complications. The independent radiologist was blinded to the intervention, product, and surgeon information. Two hundred and twenty-six (226) patients received OsteoAMP with autologous local bone, while ninety-five (95) patients received Infuse with autologous local bone. Patients underwent radiographs (x-ray and/or CT) at standard postoperative follow-up intervals of approximately 1, 3, 6, 12, and 18 months. Fusion was defined as radiographic evidence of bridging across endplates, or bridging from endplates to interspace disc plugs. Osteobiologic surgical supply costs were also analyzed to ascertain cost differences between OsteoAMP and rhBMP-2. Results OsteoAMP produced higher rates of fusion at 6, 12, and 18 months (p ≤ 0.01). The time required for OsteoAMP to achieve fusion was approximately 40% less than rhBMP-2 with approximately 70% fewer complications. Osteobiologic supply costs were 80.5% lower for OsteoAMP patients (73.7% lower per level) than for rhBMP-2. Conclusions Results of this study indicate that OsteoAMP is a viable alternative to rhBMP-2 both clinically and economically when used in TLIF and LLIF spine procedures.

Ten percent of the 250,000 proximal femur fractures that occur in the United States each year are malreduced into a varus position after treatment. Currently, there is no cephalomedullary nail available that allows the physician to dynamically change the lag-screw-to-nail angle. The Variable Angle Nail (VAN) was designed to allow movement of the lag screw relative to the shaft of the nail. This study compared the characteristics of the VAN to the Gamma 3 nail via finite element analysis (FEA) in stiffness and fatigue. The results of the FEA model with the same loading parameters showed the Gamma 3 and the VAN with lag-screw-to-nail angle of 120° to have essentially the same stiffness values ranging from 350 to 382 N/mm. The VAN with lag-screw-to-nail angles of 120°, 130°, and 140° should be able to withstand more than 1,000,000 cycles from 1,400 N to 1,500 N loading of the tip of the lag screw. The Gamma 3 should be able to last more than 1,000,000 cycles at 1,400 N. In summary, the VAN is superior or equivalent in stiffness and fatigue when compared to the Gamma 3 using FEA.

Background context Few studies exist for magnetic resonance imaging (MRI) issues and ballistics, and there are no studies addressing movement, heating, and artifacts associated with ballistics at 3-tesla (T). Movement because of magnetic field interactions and radiofrequency (RF)-induced heating of retained bullets may injure nearby critical structures. Artifacts may also interfere with the diagnostic use of MRI. Purpose To investigate these potential hazards of MRI on a sample of bullets and shotgun pellets. Study design Laboratory investigation, ex vivo. Methods Thirty-two different bullets and seven different shotgun pellets, commonly encountered in criminal trauma, were assessed relative to 1.5-, 3-, and 7-T magnetic resonance systems. Magnetic field interactions, including translational attraction and torque, were measured. A representative sample of five bullets were then tested for magnetic field interactions, RF-induced heating, and the generation of artifacts at 3-T. Results At all static magnetic field strengths, non–steel-containing bullets and pellets exhibited no movement, whereas one steel core bullet and two steel pellets exhibited movement in excess of what might be considered safe for patients in MRI at 1.5-, 3- and 7-Tesla. At 3-T, the maximum temperature increase of five bullets tested was 1.7°C versus background heating of 1.5°C. Of five bullets tested for artifacts, those without a steel core exhibited small signal voids, whereas a single steel core bullet exhibited a very large signal void. Conclusions Ballistics made of lead with copper or alloy jackets appear to be safe with respect to MRI-related movement at 1.5-, 3-, and 7-T static magnetic fields, whereas ballistics containing steel may pose a danger if near critical body structures because of strong magnetic field interactions. Temperature increases of selected ballistics during 3-T MRI was not clinically significant, even for the ferromagnetic projectiles. Finally, ballistics containing steel generated larger artifacts when compared with ballistics made of lead with copper and alloy jackets and may impair the diagnostic use of MRI.

Objectives Measuring the neck-shaft angle (NSA) and amount of shortening of the femoral neck on the anterior to posterior (AP) X-ray is important when treating proximal femur fractures. To compensate for proximal femoral external rotation, the X-rays need to be taken with the leg internally rotated, an act that cannot always be performed or verified. This study aims to define the utility of in situ AP X-ray in NSA and shortening measurements. Methods Computed tomography (CT) scans of 50 patients undergoing abdominal CT scans were assessed for the in situ rotation of the femoral neck relative to the AP beam. Three proximal femur fracture Sawbones models were made and AP X-rays of the models were taken with changing proximal femur rotation. NSA and shortening were measured on all X-rays. Results In situ femoral neck rotation averaged 25.4 ± 10.6° of external rotation (range, 0.9–51.8°, 80% of measurements less than 35°). NSA measurements varied less than 5° with less than 35° of rotation in all models, and were always greater than the true value. Femoral neck vertical length (VL) measurement was independent of proximal femur rotation whereas the horizontal length component was found to be highly dependent on the same. Conclusions NSA measured on AP X-ray will be accurate to within 5° in 80% of patients with the hip left in situ and in 100% of the patients if the hip is internally rotated 15°. Measurement of significant varus or loss of VL of the femoral neck can be considered accurate regardless of leg rotation at the time of X-rays being taken.

Pseudoarthrosis after pedicle subtraction osteotomy (PSO) can require revision surgery due to posterior rod failure, and the stiffness of these revision constructs has not been quantified.To compare the multidirectional bending stiffness of 7 revision strategies following rod failure.Seven fresh-frozen human spines (T11-pelvis) were tested as follows: (1) posterior instrumentation from T12-S1 (excluding L3) with iliac fixation and L3 PSO; (2) inline connectors after rod breakage at L3 (L2 screws removed for access); (3) cross-links connecting rods above and below inline connectors; satellite rods (4) parallel, (5) 45° anterior, and (6) 45° posterior to original rods; 45° posterior with cross-links connecting (7) original and (8) satellite rods. Groups 3 to 8 were tested in random order. Nondestructive pure moment flexion-extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted to 7.5 Nm; 3D motion tracking monitored the primary range of motion.Addition of inline connectors alone restored stiffness in FE and LB (P.05), but not in AR (P.05). Satellite rods (groups 4 to 6) restored stiffness in FE and LB (P.05), but not in AR (P.05) and were not significantly different from one another (P.05). The addition of cross-links (groups 3, 7, and 8) restored stiffness in all bending modes (P.05) and were significantly greater than inline connectors alone in AR (P.05).The results suggest that these revision strategies can restore stiffness without entire rod replacement. Failure of AR stiffness restoration can be mitigated with cross-links. The positioning of the satellite rods is not an important factor in strengthening the revision.

STUDY DESIGN: Biomechanical laboratory research. OBJECTIVE: To characterize the structural stiffness of opening and closing wedge osteotomies and the independent effect of rod diameter. SUMMARY OF BACKGROUND DATA: Traditionally, C7 opening wedge osteotomy (OWO) has been performed for patients with ankylosing spondylitis. For patients without ankylosing spondylitis, closing wedge osteotomy (CWO) may be considered for more controlled closure. Biomechanical characteristics of the two osteotomy alternatives have not yet been analyzed. METHODS: Nondestructive pure moment flexion/extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted to 4.5 Nm on cadaveric specimens (C4-T3). All specimens underwent posterior bilateral screw-rod fixation with 3.5 mm and 4.5 mm Ti rods, whereas half received OWO and half received CWO. RESULTS: Independent of osteotomy type, constructs with 4.5 mm rods exhibited a significant increase in stiffness compared to 3.5 mm rods in all bending modes (P < 0.01). Relative to 3.5 mm rods, 4.5 mm constructs showed an increase in stiffness of 31 ± 12% for FE, 37 ± 39% for LB, and 31 ± 11% for AR. At the osteotomy site, there was a 43 ± 23% increase in FE stiffness, 45 ± 36% in LB, and 41 ± 17% in AR. Independent of rod diameter, CWO was significantly stiffer than OWO (42% for the construct and 56% across the osteotomy) in FE bending only (P < 0.05). CONCLUSION: The surgeon can expect a similar increase in stiffness in switching from 3.5 mm to 4.5 mm rod independent of osteotomy type. The increased stiffness of CWOs has an anatomic basis. OWOs disrupt the anterior longitudinal ligament (ALL) and leave a significant anterior gap whereas CWOs create a wedge through the vertebral body and leave the ALL and the discs above and below the osteotomy intact. The closure in CWOs leaves no anterior gap providing greater axial loading stability. This greater bone on bone contact in CWOs is likely a significant reason for the anterior stiffness and may provide greater fusion rates in the nonankylosing spondylitis patient population.

This study compared the biomechanical fatigue strength of calcium phosphate augmented repairs versus autogenous bone graft (ABG) repairs in lateral tibia plateau fractures.Eight matched pairs of tibias (six male, two female; age, 75 ± 14 years) were harvested from fresh-frozen cadavers. Reproducible split-depression fractures were simulated and repaired by an orthopaedic traumatologist using a lateral tibial plateau plate. One tibia from each donor was randomly assigned to either calcium phosphate (Callos; Acumed, Hillsboro, OR) or ABG as augmentation. The femoral component of a hemitotal knee arthroplasty was attached to the actuator of a servohydraulic press and centered above the repair site. Cyclic, physiological compression loads were applied at 4Hz starting with a maximum load of 15% body weight and increasing by 15% body weight every 70,000 cycles. Loading conditions were determined from calculations of weight distribution, joint contact area, and gait characterization from existing literature. Repair site depression and stiffness were measured at regular intervals. Specimens were then loaded to failure at 1 mm/min.Calcium phosphate augmented repairs subsided less and were more stiff during the fatigue loading than were ABG repairs at the 70,000, 140,000, and 210,000 cycle intervals (P0.03) All repairs survived to 210,000 cycles. The average ultimate load of the calcium phosphate repairs was 2241 ± 455 N (N = 6) and 1717 ± 508 N (N = 8) for ABG repairs (P = 0.02).Calcium phosphate repairs have significantly higher fatigue strength and ultimate load than ABG repairs and may increase the immediate weightbearing capabilities of the repaired knee.

Ankylosing spondylitis (AS) is a genetic condition that frequently results in spinal sagittal plane deformity of thoracolumbar or cervicothoracic junctions. Generally, a combination of osteotomy and spinal fixation is used to treat severe cases. Although surgical techniques for traumatic injury across the cervicothoracic junction have been well characterized in clinical and biomechanical literature, the specific model of instrumented opening wedge osteotomy in autofused AS has not been studied biomechanically. This study characterizes the structural stability of various posterior fixation techniques across the cervicothoracic junction in spines with AS, specifically considering the effects of posterior rod diameter and material type.For each of 10 fresh-frozen human spines (3 male, 7 female; mean age 60 ± 10 years; C3-T6), an opening wedge osteotomy was performed at C7-T1. Lateral mass screws were inserted bilaterally from C-4 to C-6 and pedicle screws from T-1 to T-3. For each specimen, 3.2-mm titanium (Ti), 3.5-mm Ti, and 3.5-mm cobalt chromium (CoCr) posterior spinal fusion rods were tested. To simulate the anterior autofusion and long lever arms characteristic of AS, anterior cervical plates were placed from C-4 to C-7 and T-1 to T-3 using fixed angle screws. Nondestructive flexion-extension, lateral bending, and axial rotation tests were conducted to 3.0 Nm in each anatomical direction; 3D motion tracking was used to monitor primary range of motion across the osteotomy (C7-T1). Biomechanical tests used a repeat-measures test design. The order of testing for each rod type was randomized across specimens.Constructs instrumented with 3.5-mm Ti and 3.5-mm CoCr rods were significantly stiffer in flexion-extension than those with the 3.2-mm Ti rod (25.2% ± 16.4% and 48.1% ± 15.3% greater than 3.2-mm Ti, respectively, p0.05). For axial rotation, the 3.5-mm Ti and 3.5-mm CoCr constructs also exhibited a significant increase in rigidity compared with the 3.2-mm Ti construct (36.1% ± 12.2% and 52.0% ± 20.0%, respectively, p0.05). There were no significant differences in rigidity seen between the 3 types of rods in lateral bending (p0.05). The 3.5-mm CoCr rod constructs showed significantly higher rigidity in flexion-extension than the 3.5-mm Ti rod constructs (33.1% ± 15.5%, p0.05). There was a trend for 3.5-mm CoCr to have greater rigidity in axial rotation (36.2% ± 18.6%), but this difference was not statistically significant (p0.05).The results of this study suggest that 3.5-mm CoCr rods are optimal for achieving the most rigid construct in opening wedge osteotomy in the cervicothoracic region of an AS model. Rod diameter and material properties should be considered in construct strategy. Some surgeons have advocated anterior plating in patients with AS after osteotomy for additional stability and bone graft surface. Although this effect was not examined in this study, additional posterior stability achieved with CoCr may decrease the need for additional anterior procedures.

Ankylosing spondylitis is a genetic condition [1] that frequently results in spinal sagittal plane deformity of thoracolumbar or cervicothoracic junction. Generally, a combination of osteotomy and spinal fixation is used to treat severe cases of ankylosing spondylitis to restore spinal balance and horizontal gaze [2]. This study investigates the biomechanics of opening wedge osteotomy at the cervicothoracic junction. Although surgical techniques for traumatic injury across the cervicothoracic junction have been well characterized in the clinical and biomechanical literature, the specific model of instrumented opening wedge ostetomy in autofused ankylosing spondylitis has not been studied biomechanically.

Failure of the posterior rods in long thoracolumbar deformity correction cases often requires revision surgery to treat the pseudoarthrosis and prevent loss of correction. While the entire rod can be replaced, this involves opening the entire incision which can lead to increased morbidity. Other clinically advantageous options include minimally invasive surgical approaches such as percutaneous insertion of connectors and additional rods.Copyright © 2010 by ASME

Both expandable and non-expandable interbody cage designs are available to surgeons for cases involving spinal reconstruction and stabilization following single level lumbar corpectomy [1]. Different expandable cage designs are on the market [2], but all involve a manual mechanism to intraoperatively adjust the compressive load applied by the cage against the vertebral body endplates. Non-expandable cages do not have such a mechanism, and surgeons rely on cutting the cage to the appropriate length to achieve a “press-fit.” The clinical reasoning behind the expandable cage design is that the adjustability of the device will allow the surgeon to achieve the maximum contact area between the cage and the vertebral endplate without “overstuffing” the interbody space and thus causing a sagittal-plane deformity.Copyright © 2010 by ASME

Sagittal imbalance of the cervicothoracic spine often causes severe pain and loss of horizontal gaze. Traditionally, C7 opening wedge osteotomy has been classically performed for patients with ankylosing spondylitis. For patients without ankylosing spondylitis closing wedge osteotomy may be considered for more controlled closure. Biomechanical characteristics of the two osteotomy alternatives have not yet been analyzed. The goal of this study is to characterize the structural stability of the two types of cervicothoracic junction osteotomies and the independent effect of rod diameter.Copyright © 2010 by ASME