Posterior atlantoaxial fixation of osteoporotic odontoid fracture: biomechanical analysis of the Magerl versus harms techniques in a cadaver model.

BACKGROUND CONTEXT: Odontoid fractures are among the most common cervical spine fractures in the elderly and are associated with increased morbidity and mortality. Clinical evidence suggests improved survival and quality of life after operative intervention compared to nonoperative treatment. PURPOSE: This study seeks to examine the stability of an osteoporotic Type II odontoid fracture following posterior atlantoaxial fixation with either the Magerl transarticular fixation technique or the Harms C1 lateral mass screws C2 pedicle screw rod fixation. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Eighteen cadaveric specimens extending from the cephalus to C7 were used in this study. Reflective marker arrays were attached to C1 and C2 and a single marker on the dens to measure movement of each during loading with C2-C3 and occiput-C1 being allowed to move freely. A biomechanical testing protocol imparted moments in flexion-extension, axial rotation, and lateral bending while a motion capture system recorded the motions of C1, C2, and the dens. The spines were instrumented with either the Harms fixation (n=9) or Magerl fixation (n=9) techniques, and a simulated Type II odontoid fracture was created. Motions of each instrumented spine were recorded for all moments, and then again after the instrumentation was removed to model the injured, noninstrumented state. RESULTS: Both Harms and Magerl posterior C1-C2 fixation allowed for C1, C2, and the dens to move as a relative unit. Without fixation the dens motion was coupled with C1. No significant differences were found in X, Y, Z translation motion of the dens, C1 or C2 during neutral zone motions between the Magerl and Harms fixation techniques. There were no significant differences found in Euler angle motion between the two techniques in either flexion-extension, axial rotation, or lateral bending motion. CONCLUSIONS: Our findings suggest that both Harms and Magerl fixation can significantly reduce dens motion in Type II odontoid fractures in an osteoporotic cadaveric bone model. CLINICAL SIGNIFICANCE: Both Harms and Magerl posterior atlantoaxial fixation techniques allowed for C1, C2, and the dens to move as a relative unit following odontoid fracture, establishing more anatomic stability to the upper cervical spine.

The Effect of Povidone-Iodine Irrigation on the Efficacy of Antibiotic Cement In Vitro.

Povidone-iodine is a common antiseptic demonstrating success in reducing infection rates in primary arthroplasty; however, recent data suggest that its use in revision arthroplasty may increase infection rates. This study evaluated the effect of povidone-iodine solution on antibiotic cement and investigated the connection between povidone-iodine and increased infection rates in revision arthroplasty. Sixty antibiotic cement samples (ACSs) were formed using gentamicin-impregnated cement. The ACSs were divided into three groups: group A (n=20) was subject to a 3-minute povidone-iodine soak followed by a saline rinse; group B (n=20) underwent a 3-minute saline soak; and group C (n=20) underwent only a saline rinse. The antimicrobial activity of the samples was tested using a Kirby-Bauer-like assay using Staphylococcus epidermidis. The zone of inhibition (ZOI) was measured every 24 hours for 7 days. All groups possessed the greatest antimicrobial activity at 24 hours. Group C displayed a mass-corrected ZOI of 395.2 mm/g, which was statistically greater than the group B ZOI (313.2 mm/g, P<.05) but not the group A ZOI (346.5 mm/g, P>.05). All groups demonstrated a decrease in antimicrobial activity at 48 through 96 hours, with no significant difference at any time point. Prolonged soaking of antibiotic cement in a povidone-iodine or saline solution results in elution of the antibiotic into the irrigation solution, blunting initial antibiotic concentration. When using antibiotic cement, antiseptic soaks or irrigation should be focused prior to cementation. [Orthopedics. 2024;47(1):10-14.].

Utility of Repeat MRI in Patients With Degenerative Cervical Disease.

Existing guidelines regarding indications for initial cervical spine magnetic resonance imaging (MRI) do not indicate when to perform repeat MRI in patients with previously documented degenerative disease. This study evaluates the efficacy of repeat MRI in patients with previously diagnosed degenerative cervical disease. Between 2013 and 2018, 153 patients (102 women, 51 men; mean age, 55 years; range, 19-81 years) without a history of trauma or surgery underwent cervical spine MRI 2 or more times at our institution indicated for symptoms of neck pain with or without radiculopathy. The MRI reports of repeat studies were reviewed and compared with index studies for notable changes. Notable radiographic changes were defined as any progression of the existing degenerative disease. Fifty-three of 153 (35%) patients demonstrated progression on repeat MRI. Forty-nine of the 53 patients demonstrating progression had new or worsening symptoms prior to their follow-up study (P=.03). Twenty-nine of 35 (83%) patients with new or worsening radiculopathy progressed on MRI (P<.01). Nine of 10 (90%) patients with new upper motor neuron findings demonstrated progression (P=.01). Axial neck pain alone was not statistically linked to MRI progression (P=.1). Twenty-five (16.3%) patients underwent operative management for their disease. Only 12 (48.0%) of the surgical patients presented MRI progression (P=.1). In the absence of new or worsening degenerative cervical symptoms, additional MRI studies are unlikely to reveal any radiographic progression or change clinical management from nonoperative to operative. [Orthopedics. 2023;46(2):98-102.].

Characterization of regional variation of bone mineral density in the geriatric human cervical spine by quantitative computed tomography.

BACKGROUND: Odontoid process fractures are among the most common in elderly cervical spines. Their treatment often requires fixation, which may include use of implants anteriorly or posteriorly. Bone density can significantly affect the outcomes of these procedures. Currently, little is known about bone mineral density (BMD) distributions within cervical spine in elderly. This study documented BMD distribution across various anatomical regions of elderly cervical vertebrae. METHODS AND FINDINGS: Twenty-three human cadaveric C1-C5 spine segments (14 males and 9 female, 74±9.3 y.o.) were imaged via quantitative CT-scan. Using an established experimental protocol, the three-dimensional shapes of the vertebrae were reconstructed from CT images and partitioned in bone regions (4 regions for C1, 14 regions for C2 and 12 regions for C3-5). The BMD was calculated from the Hounsfield units via calibration phantom. For each vertebral level, effects of gender and anatomical bone region on BMD distribution were investigated via pertinent statistical tools. Data trends suggested that BMD was higher in female vertebrae when compared to male ones. In C1, the highest BMD was found in the posterior portion of the bone. In C2, BMD at the dens was the highest, followed by lamina and spinous process, and the posterior aspect of the vertebral body. In C3-5, lateral masses, lamina, and spinous processes were characterized by the largest values of BMD, followed by the posterior vertebral body. CONCLUSIONS: The higher BMD values characterizing the posterior aspects of vertebrae suggest that, in the elderly, posterior surgical approaches may offer a better fixation quality.

Relationship to drill bit diameter and residual fracture resistance of the distal tibia.

BACKGROUND: The etiology of bone refractures after screw removal can be attributed to residual drill hole defects. This biomechanical study compared the torsional strength of bones containing various sized cortical drill defects in a tibia model. METHODS: Bicortical drill hole defects of 3 mm, 4 mm, and 5 mm diameters were tested in 26 composite tibias versus intact controls without a drill defect. Each tibia was secured in alignment with the rotational axis of a materials testing system and the proximal end rotated internally at a rate of 1 deg./s until mechanical failure. FINDINGS: All defect test groups were significantly lower (P < 0.01) in torque-to-failure than the intact group (82.80 ± 3.70 Nm). The 4 mm drill hole group was characterized by a significantly lower (P = 0.021) torque-to-failure (51.00 ± 3.27 Nm) when compared to the 3 mm drill hole (59.00 ± 5.48 Nm) group, but not different than the 5 mm hole group (55.71 ± 5.71 Nm). All bones failed through spiral fractures, bones with defects also exhibited posterior butterfly fragments. INTERPRETATION: All the tested drill hole sizes in this study significantly reduced the torque-to-failure from intact by a range of 28.4% to 38.4%, in agreement with previous similar studies. The 5 mm drill hole represented a 22.7% diameter defect, the 4 mm drill hole a 18.2% diameter defect, and the 3 mm drill hole a 13.6% diameter defect. Clinicians should be cognizant of this diminution of long bone strength after a residual bone defect in their creation and management of patient rehabilitation programs.

How Does Tibial Pin Placement in Navigated Total Knee Arthroplasty Affect the Torsional Strength of the Tibia?

INTRODUCTION: Surgical navigation technology has recently become more prevalent for total knee arthroplasty. Surgical navigation typically requires pin placement in the proximal tibia diaphysis to stabilize the bone-tracking hardware, and there have been several recent reports of fractures through these residual navigation pin holes. The objective of this biomechanical study was to determine whether a difference exists in the torsional bone strength of a 5-mm navigation pin hole drilled at a single location in three different orientations: unicortical, bicortical, and transcortical. METHODS: Biomechanical composite sawbone tibias were used to test four conditions: the intact condition with no holes, a unicortical hole, a bicortical hole, and a transcortical hole through the proximal diaphysis. Seven specimens from each group were tested in external rotation to failure at 1 deg/sec. Torque-to-failure, absorbed energy-to-failure, and rotational angle-to-failure were statistically compared across the four groups. RESULTS: All specimens failed proximally by spiral oblique fractures. No statistical differences were found between unicortical and bicortical groups in torque-to-failure, energy-to-failure, and angle-to-failure. However, both unicortical and bicortical groups were markedly lower in all measures than the intact group. The transcortical group was markedly lower in all measures than the intact group and both unicortical and bicortical groups. DISCUSSION: An appropriately placed navigation residual pin hole, either unicortical or bicortical, markedly decreases the torque-to-failure, energy-to-failure, and angle-to-failure of the tibia compared with the intact condition in a synthetic sawbones model. No notable difference was detected between the unicortical and bicortical holes; however, an errant transcortical residual navigation pin hole markedly decreases all measures compared with an appropriately placed unicortical or bicortical hole.

The Legal, Ethical, and Scientific Considerations for Returning Explanted Orthopaedic Hardware to the Patient.

ABSTRACT: Orthopaedic hardware explantation is a multifaceted topic with complex legal, ethical, and scientific aspects that require thorough exploration. Issues of device ownership, explant-induced disease propagation, and potential device resale pose legal risks to providers and health-care institutions. Ethically, implant removal highlights the potential that performing procedures at the request of the patient will incentivize patient compliance and strengthen the patient-surgeon relationship. However, the return of explanted hardware to patients could hinder scientific study and innovation, ultimately limiting advancement in risk reduction and patient outcomes. Continued research into these topics remains paramount to ensure that clinicians and institutions deliver optimal patient care while abiding with legal and ethical imperatives. This article addresses the legal, ethical, and scientific issues that are pertinent to returning an explanted orthopaedic implant to the patient and the potential ramifications of such practice.

Diabetes Mellitus Blunts the Symptoms, Physical Function, and Health-Related Quality of Life Benefits of Total Knee Arthroplasty: A Systematic Review With Meta-analysis of Data From More Than 17 000 Patients.

OBJECTIVE: To compare physical function, pain, impairments (stiffness, range of motion, and strength), and health-related quality of life (HRQoL) outcomes between patients with and without diabetes mellitus, before and after a total knee arthroplasty (TKA). DESIGN: Prognosis systematic review. LITERATURE SEARCH: We searched MEDLINE/PubMed, CINAHL, SPORTDiscus, and Web of Science to August 2019. STUDY SELECTION CRITERIA: We included longitudinal studies that examined physical function, pain, impairments, and HRQoL outcomes among patients receiving a TKA and with or without diabetes. DATA SYNTHESIS: For quantitative synthesis, we stratified outcomes based on time relative to TKA: preoperative, less than 1 year after a TKA (early postoperative), and 1 year or more after a TKA (late postoperative). We used random-effects meta-analysis to calculate standardized mean differences (SMDs) and 95% confidence intervals (CIs). We used the Grading of Recommendations Assessment, Development and Evaluation system for qualitative synthesis. RESULTS: We included 21 studies (n = 17 472 patients). Patients with diabetes mellitus had worse preoperative physical function (SMD, -0.16; 95% CI: -0.24, -0.08) and HRQoL (SMD, -0.16; 95% CI: -0.26, -0.05), worse early postoperative pain (SMD, -0.22; 95% CI: -0.39, -0.05) and strength (SMD, -0.45; 95% CI: -0.77, -0.14), and worse late postoperative physical function (SMD, -0.23; 95% CI: -0.40, -0.06), range of motion (SMD, -0.23; 95% CI: -0.46, 0.00), and HRQoL (SMD, -0.19; 95% CI: -0.29, -0.08) than patients without diabetes mellitus. The overall risk of bias across studies was high, and the certainty of evidence ranged from low to very low. CONCLUSION: Patients with diabetes mellitus had worse patient-reported and clinician-assessed outcomes before and after a TKA. Given the limitations of included studies, these results may change with future research. J Orthop Sports Phys Ther 2021;51(6):269-280. Epub 19 Apr 2021. doi:10.2519/jospt.2021.9515.

Identifying risk factors for missed compartment syndrome in patients with tibia shaft fractures: An analysis of the national trauma data bank.

OBJECTIVES: Acute compartment syndrome (CS) is a common complication of tibia shaft fractures (TSFs), and occurs when the pressure inside a myofascial compartment rises and impairs tissue perfusion. If treatment is delayed due to a missed diagnosis, amputation or permanent loss of function can result. This study aims to determine the incidence, clinical associations, and risk factors for missed CS following surgical stabilization of tibia shaft fractures (TSFs) using data from the National Trauma Data Bank (NTDB). METHODS: NTDB data files from 2007 to 2016 were accessed to collect information on patients undergoing surgical fixation of TSFs. Patients with an Injury Severity Score (ISS) > 15 or inferred Gustilo-Anderson IIIB/IIIC fractures were excluded to create a more homogenous sample of lower-grade TSFs. Compartment syndrome that was originally missed leading to late intervention was the main outcome under investigation. Bivariate tests were used to assess the relationships between missed CS and the preoperative variables. If a variable and a complication had an association with a P ≤ 0.2, it was included in a multivariate logistic regression model. RESULTS: A total of 184,612 patients met our inclusion criteria, and 1,269 patients (0.76%) had a missed CS diagnosis. Bivariate analysis demonstrated that male gender had a significant positive association with a missed CS diagnosis, while older age had a significant negative association (odds ratio [OR] = 2.17, 0.99; P < 0.001). Multivariate analysis revealed that male gender was the most significant independent risk factor for a missed diagnosis of compartment syndrome (OR = 1.84, P < 0.00001), followed by alcoholism, penetrating trauma, and smoking (OR = 1.51, 1.46, 1.43; P < 0.02). The only significant protective factor was open fracture (OR = 0.70, P < 0.0001). CONCLUSIONS: Our research identified several significant risk factors for missed CS after TSF, as well as positive and negative associations. Male gender, age, and lifestyle choices such as alcohol use and smoking conferred increased risks. These variables may assist physicians in identifying at-risk patients who may benefit from increased monitoring, and potentially prevent the high morbidity associated with this condition.

Serial Surgical Debridement and Fixation of Chronic Pelvis Instability Secondary to Pubic Symphysis and Sacroiliac Osteomyelitis: A Case Report.

Introduction: Chronic global pelvic instability can be due to many different etiologies with infection being an uncommon cause. We present a case of chronic global pelvis instability secondary to osteomyelitis involving both the anterior and posterior ring, a rare and challenging problem with no standard treatment. Case Presentation: A 57-year-old female with a history of intravenous drug use presented with global pelvis instability in the setting of pubic symphysis and posterior sacroiliac osteomyelitis with multiple-associated abscesses. She was managed with serial surgical debridement's X4 and combined anterior and posterior fixation/fusion, with resolution of her infection and instability. Conclusions: This is the first reported case of chronic pelvis instability secondary to anterior and posterior pelvic ring osteomyelitis that was successfully treated with serial debridement and combined anterior and posterior fixation/fusion.

Effects of Lumbosacral Arthrodesis on the Biomechanics of the Sacroiliac Joint.

BACKGROUND: It is unclear whether the sacroiliac joint is vulnerable to adjacent segment disease. Clinical studies have suggested that many patients who have undergone lumbar arthrodesis will develop adjacent segment disease, which may contribute to sacroiliac joint degeneration. The purpose of the present study was to examine whether arthrodesis in the lumbar spine results in altered biomechanics at the sacroiliac joint that could contribute to adjacent segment disease within the joint. METHODS: With use of human cadavers in a biomechanical laboratory study, the effects of lower-lumbar arthrodesis and sacroiliac screws on the biomechanics of the sacroiliac joint were assessed. Human cadaveric pelves with lumbar spines were biomechanically tested in flexion-extension, rotation about the vertical axis, and compression along the vertical axis with single and double-leg support. Four conditions were compared: (1) intact, (2) L4-L5 arthrodesis, (3) L4-S1 arthrodesis, and (4) left sacroiliac screw. Construct vertical and horizontal motions at the anterior and posterior surfaces of the sacroiliac joint were measured. RESULTS: Significant measurable increases in motion of the sacroiliac joint related to arthrodesis of the lumbar spine occurred with flexion-extension loading (p < 0.05). No significant changes were observed for rotation about the vertical axis or compression along the vertical axis with single and double-leg support. CONCLUSIONS: After 360°, 1 or 2-level lumbosacral spine arthrodesis, the sacroiliac joint showed a significant increase in rotational motion with flexion-extension loading. Increases in horizontal translation with axial rotation loading and vertical translation with axial compression loading were not significant. CLINICAL RELEVANCE: The risk of significant alteration of normal sacroiliac kinematics should be considered in all patients undergoing 360° lumbosacral arthrodesis.

Cerclage Cable Tensioning of Intraoperative Hip Arthroplasty Proximal Femoral Fractures: A Cadaveric Model.

Cerclage fixation following intraoperative fracture of the proximal femur during total hip arthroplasty (THA) carries a risk of compromising the femoral blood supply. Thus, we sought to determine the minimum cerclage cable tension required to restore the stability of a cementless femoral stem. Cementless femoral prostheses were implanted in seven proximal femoral cadaver specimens, and a periprosthetic fracture was simulated in the medial cortex. A single cerclage cable was placed just above the lesser trochanter and tensioned and tested at increasing intervals. The implant's torsional stability was determined in the intact bone, prior to fixation, and at each level of cable tension. We found that a single cerclage cable placed above the lesser trochanter can significantly improve, but not fully restore, torsional stability following intraoperative periprosthetic femur fracture during THA. The optimal position for a single cerclage cable appears to be above the lesser trochanter. (Journal of Surgical Orthopaedic Advances 29(4):209-211, 2020).

Rater Variation in Ultrasound Detection of Dorsal Cortex Screw Protrusion in Fixed-Angle Volar Plating of the Distal Radius.

This study evaluates rater accuracy and variation for the purpose of using intraoperative ultrasound (US) imaging to detect dorsal screw protrusion during fixed-angle volar plating of distal radius fractures. Stabilizing volar plates and screws with varying lengths of dorsal protrusion were applied to 10 cadaver wrist pairs. After a brief training session, seven surgeons without prior ultrasound experience assessed screw protrusion on two separate occasions using a diagnostic ultrasound machine. Screw protrusions were visually confirmed after data collection was completed. Statistical analyses included percent agreement and Cohen's kappa for accuracy and intra- and inter-rater reliability, sensitivity, specificity, and positive and negative predictive values. Only two out of seven raters met acceptable levels of accuracy and consistency. Our findings inform us that accuracy and consistency of ultrasound-guided detection of dorsal screw protrusion are negatively impacted by rater variation. Further investigations are needed to improve rater effectiveness. (Journal of Surgical Orthopaedic Advances 28(4):260-267, 2019).

Biomechanical Evaluation of Dual Plate Configurations for Femoral Shaft Fracture Fixation.

AIM: This study aimed at comparing the mechanical properties of conventional and locking dual plates in adjacent and orthogonal orientations for the surgical fixation of transverse femoral shaft fractures. It also assessed the failure mechanics after dual adjacent and orthogonal locking plate removal. METHODS: Thirty-two composite femurs were transversally osteotomized and randomly assigned for fixation with either dual locking or compression plates in an adjacent or orthogonal configuration. Sixteen specimens were preloaded axially to 20 N and single-leg stance loads were simulated. The remaining sixteen constructs were subjected to torsional loads of 10 Nm at a rate of 10 Nm/s in external and internal rotation of the femoral head in relation to the knee. Overall combined rotational stiffness was calculated. Eight different specimens with no osteotomy underwent the same experiments after dual locked plate removal and were tested to failure in combined eccentric axial and torsional modes. Data were statistically processed using a two-tailed t-test and one-way analysis of variance for the comparison of means between two or more groups, respectively. RESULTS: Orthogonal constructs were statistically stiffer in axial loading compared to their adjacent counterparts in both conventional and locking configurations (p<0.001). Dual locking plates provided higher torsional stiffness than conventional ones within each plate orientation (p<0.01). Neither axial/torsional strength nor failure loads differed between constructs that had adjacent or orthogonal dual locking plates instrumented and then removed (p>0.05). CONCLUSIONS: In both orthogonal and adjacent orientations, double locking plates provide higher stability than their dual conventional counterparts. Orthogonal dual plate configuration is more stable and biomechanically superior to dual adjacent plating for constructs fixed with either standard compression or locking plates.

Impact of orthopaedic candidate interview timing on successful matching.

INTRODUCTION: The impact of the interview date on matching in orthopaedic surgery residency is unknown. MATERIALS AND METHODS: A retrospective review of interviewed applicants for a first-year orthopaedic surgery residency was conducted to determine the likelihood of matching based on being interviewed early versus late at our program. The United States Medical Licensing Examination (USMLE) scores were compared between early and late interviewees. RESULTS: Between 2012 and 2016, 316 candidates interviewed for residency positions. Twenty matched at our program and 230 at other institutions. No difference existed in USMLE scores. Late interviewees had significantly higher chances of matching at our center, but not nationwide in orthopaedic surgery (p = 0.025 and p = 0.58, respectively). CONCLUSION: Later applicant interview was associated with greater chance of matching at our institution, but did not impact the candidate's ability to match in orthopaedic surgery at other programs.