Osseous Defects Research Articles

Staged revision of the infected knee arthroplasty and endoprosthesis.

Periprosthetic joint infection (PJI) is a challenging complication of any arthroplasty procedure. We reviewed our use of static antibiotic-loaded cement spacers (ABLCSs) for staged management of PJI where segmental bone loss, ligamentous instability, or soft-tissue defects necessitate a static construct. We reviewed factors contributing to their failure and techniques to avoid these complications when using ABLCSs in this context. A retrospective analysis was conducted of 94 patients undergoing first-stage revision of an infected knee prosthesis between September 2007 and January 2020 at a single institution. Radiographs and clinical records were used to assess and classify the incidence and causes of static spacer failure. Of the 94 cases, there were 19 primary total knee arthroplasties (TKAs), ten revision TKAs (varus-valgus constraint), 20 hinged TKAs, one arthrodesis (nail), one failed spacer (performed elsewhere), 21 distal femoral endoprosthetic arthroplasties, and 22 proximal tibial arthroplasties. A total of 35/94 patients (37.2%) had spacer-related complications, of which 26/35 complications (74.3%) were because of mechanical failure of the spacer construct, while 9/35 (25.7%) were due to recurrence of infection. Risk factors for internal failure were a construct where the total intramedullary spacer length was less than twice the length of the central osseous defect (p = 0.009), where proximal or distal intraosseous spacer contact was < 10%, and after tibial tubercle osteotomy (p = 0.005). The incidence of spacer complications significantly increased the time to second stage: mean 157 days (42 to 458) in those without complications versus 227 days (11 to 528) with complications (p = 0.014). The failure rate of static antibiotic-loaded cement spacers is much higher than anticipated. Complications of the spacer significantly increased the time to second-stage revision. The risk of mechanical failure is significantly increased if the spacer is less than double the size of the segmental defect, or if inadequate reinforcement is inserted into the residual bone. These findings serve as a guide for surgeons to avoid mechanical complications with static spacers.

Aneurysmal bone cyst of the greater trochanter: evaluation of surgical outcome of 17 cases

Background: Aneurysmal bone cyst is a benign, aggressive lesion that occurs in childhood and early adulthood. It usually affects the metaphysis of long bones. The aims of this study were to report clinical and radiological outcome following operative treatment of aneurysmal bone cyst of greater trochanter of femur and asses functional outcome by the Musculoskeletal Tumour Society (MSTS) Rating scale for the lower extremity. Methods: This Quasi-experimental study included 17 patients radiologically and histologically diagnosed as having aneurysmal bone cyst involving the greater trochanter of femur from 2015 to 2022. All cases were curetted, chemical cauterization with 5% phenol done and autogenous cortico-cancellous bone graft were added to fill the osseous defect. The patients were followed-up at 6 weeks and then 3 monthly for 1st year, 6 monthly for 2nd and 3rd year and yearly thereafter. In each follow-up, the recurrence, post-operative complications were documented and MSTS scoring was done. Results: The mean age of the patients were 14.5 years; 9 (53%) were female and 8 (47%) were male. The mean follow-up period for the patients was 3.6 years. There were 3 (18%) recurrences and 2 (11.8%) cases developed superficial surgical site infection. The average MSTS score on final follow-up was 22.6. Conclusion: Aneurysmal bone cyst of the greater trochanter is common in second decade among females. Treatment with extended intralesional curettage, chemical cauterization with 5% phenol and application of autogenous bone graft has less than 18% chance of recurrence. Furthermore, there is acceptable radiological bone graft incorporation and average MSTS score on final follow-up suggest a good functional outcome. BIRDEM Med J 2024; 14(3): 124-130

Free Vascularized Scapula tip Flap to L5—S1 Vertebral Defect After Chronic Infection Related to Interbody Fusion Cage: A Case Report

ABSTRACTSeptic nonunion after vertebral fusion can lead to significant patient disability. The management of septic nonunions usually involves surgical debridement, bone fixation, and antibiotic therapy. Particularly challenging is lumbosacral vertebral nonunions, which necessitate a difficult surgical approach. We present a novel approach using a scapula tip free flap through an intra‐abdominal approach to reconstruct a L5–S1 vertebral defect after a septic nonunion. Our patient, 31‐year‐old man, with no medical conditions, had a fusion of L5–S1 due to severe lower back pain secondary to isthmic spondylolysis and spondylolisthesis. Despite multiple attempts of surgical fusion, postoperatively the patient developed a septic nonunion. Following a modified DAIR, the nonunion was reconstructed with a scapula tip bone flap 4 × 3 × 2 cm. The subscapular vessels were anastomosed to the deep inferior epigastric vessels after an intra‐abdominal inset. The patient was discharged at 15 days postoperatively without any complications. At 1‐year follow‐up the patient is pain‐free, off opiate analgesia with radiological evidence of fusion between the scapula tip, L5 and the S1 vertebral body. This case report describes the use, for the first time, of a free scapula tip, to a lumbosacral spinal defect. The use of the free scapula tip flap may be considered for reconstruction of osseous spinal defects due to its long pedicle and the unique bone shape.

Long-term results and patient-reported outcomes after vascularized fibular graft use in the treatment of post-traumatic bone defects of femur shaft and tibia: A retrospective cohort and cross-sectional survey study

Post-traumatic critical-sized bone defects pose a reconstructive challenge for reconstructive surgeons. The vascularized fibula graft is a well-described treatment for osseous defects of the femur and tibia. This study aimed to assess long-term patient-reported quality of life, the success-, and complication rates in lower extremity reconstruction with vascularized fibula grafts. A retrospective cohort of 29 patients who underwent fibula graft reconstruction for critical-sized bone defects after post-traumatic tibial and femoral bone loss between 1990 and 2021 was included. To assess the health-related quality of life and return to work and satisfaction, a cross-sectional survey was performed using the short-form-36, lower extremity functional scale, and a self-made questionnaire including the DN4, satisfaction, and subjective ankle function. The median bone defect size was 8cm (IQR 9-7cm). The mental component scores were comparable to the Dutch population norm, whereas the impaired physical function scores were associated with pain (r 0.849, p<0.001). Neuropathic symptoms were reported in 7 out of 19 patients, and 11 out of 19 patients returned to normal daily activity. All respondents reported positive or neutral scores on overall satisfaction with the recovery. Bone healing was uneventful in 19 out of 29 patients. Union was achieved in 25 out of 29 patients. Persistent nonunion was observed in 4 patients, leading to amputation in 2 patients. Vascularized fibula graft use led to high union rates and limb salvage in patients with post-traumatic segmental bone loss of the tibia and femur. Patient satisfaction with the overall recovery was positive; however, functional outcomes remained impaired.

A Treatment Algorithm for Free Vascularized Bone Reconstruction in Rare Large Osseous Defects Involving the Wrist.

Large bone defects of the distal radius and/or carpus following tumor resection, trauma, or infection are extremely rare. There are few case reports and series in the literature on the reconstruction approaches required in such cases. Therefore, large studies cannot be used to guide the therapeutic decisions of reconstructive plastic and hand surgeons. The objective of this study is to propose a treatment algorithm to predict the functional outcome and quality of life for the different techniques of free vascularized bone reconstruction in the interval between the distal radius, the carpus, and/or the proximal metacarpal. The algorithm was developed based on our own case studies and the few treatment approaches described in the literature. It can be applied to rare cases of massive bone defects in the wrist. The flowchart enables surgeons to develop an individualized reconstruction concept for various intervals of bone defects in the area of the distal radius and proximal metacarpal bones. Ultimately, the treatment algorithm aims to maximize future quality of life (QoL) and function of the distal upper extremity in rare cases of massive wrist-bone defects.

Quality assessment of regenerated bone in intraosseous and intramuscular scaffolds by spectroscopy and nanoindentation

The efficiency of synthetic bone grafts can be evaluated either in osseous sites, to analyze osteoconduction or ectopically, in intramuscular or subcutaneous sites, to assess osteoinduction. Bone regeneration is usually evaluated in terms of the presence and quantity of newly formed bone, but little information is normally provided on the quality of this bone. Here, we propose a novel approach to evaluate bone quality by the combined use of spectroscopy techniques and nanoindentation. Calcium phosphate scaffolds with different architectures, either foamed or 3D-printed, that were implanted in osseous or intramuscular defects in Beagle dogs for 6 or 12 weeks were analyzed. ATR-FTIR and Raman spectroscopy were performed, and mineral-to-matrix ratio, crystallinity, and mineral and collagen maturity were calculated and mapped for the newly regenerated bone and the mature cortical bone from the same specimen. For all the parameters studied, the newly-formed bone showed lower values than the mature host bone. Hardness and elastic modulus were determined by nanoindentation and, in line with what was observed by spectroscopy, lower values were observed in the regenerated bone than in the cortical bone. While, as expected, all techniques pointed to an increase in the maturity of the newly-formed bone between 6 and 12 weeks, the bone found in the intramuscular samples after 12 weeks presented lower mineralization than the intraosseous counterparts. Moreover, scaffold architecture also played a role in bone maturity, with the foamed scaffolds showing higher mineralization and crystallinity than the 3D-printed scaffolds after 12 weeks.

Periodontal Osseous Defects: A Treatment-Oriented Classification to Guide Regenerative Treatment Planning.

Periodontal bony defects are classified into 'supraosseous' ('suprabony') or 'infraosseous' ('infrabony') according to the location of the base of the defect compared to the coronal part of the residual alveolar crest. Infraosseous defects are generally considered more challenging to treat and are thought to be associated with a higher risk of periodontal progression. The emergence and advancement of periodontal regenerative procedures have improved the clinician's ability to manage infraosseous defects. However, limitations still exist. This paper reviews the definitions of periodontal osseous defects and provides a new classification framework for infraosseous defects, relating them to the chances of success of regenerative procedures and therefore to their treatment planning options. Infraosseous defects are hereby divided into intrabony and inter-root defects. Factors affecting treatment response, such as number of walls, depth and extension into buccal and lingual surfaces are added to the classification framework.

Periodontal plastic surgery and regenerative periodontal surgery in a forty-seven-year-old patient with cleft lip and palate

Cleft lip and palate represent one of the most prevalent congenital malformations in humans, with an estimated prevalence of 0.45 per 1,000 individuals. During childhood and adolescence, affected patients undergo lengthy and complicated interdisciplinary treatment including treatment from specialists in pediatric medicine, oral and maxillofacial surgery, orthodontics, and otorhinolaryngology. The patient exhibited scarred adhesions with localized mucogingival deformities of the premaxilla (region 12 − 11), bilateral cleft lip and palate, and a complex underlying one-wall intrabony osseous defect on tooth 11, in addition to hard- and soft-tissue deficiencies at the dental implant in region 12. Following the administration of localized anti-infective periodontal therapy, regenerative periodontal surgery, regenerative surgical therapy of periimplantitis, and periodontal plastic surgery were performed. This resulted in a long-term, stable improvement in the clinical situation. Regenerative periodontal therapy and periodontal plastic surgery in patients with palato-alveolar cleft present a significant challenge due to the poor condition of the mucosa and gingiva adjacent to the defect and the insufficient bone dimensions. For this reason, it seems beneficial to include the periodontist in the interdisciplinary treatment team of a patient with cleft lip and palate from the outset. It is recommended that the patient be provided with dental prophylaxis measures and receive individualized oral hygiene instructions in addition to the main maxillofacial and orthodontic treatment. This approach would facilitate the identification of mucogingival issues at an early stage and the implementation of appropriate treatment.

Treatment of periodontal osseous defect with bio-oss xenograft and biodegradable IGF fibers: A case report

Osseous defect caused due to periodontitis needed to be repaired or regenerated to avoid tooth loss. Bio-oss is made up of 10% porcine collagen and can induce osteoblastic differentiation due to its volumetric stability and out standing osteoconductive properties. Application of growth factors in regenerative procedures have helped to maintain the scaffold and induce several cellular processes. The biodegradable fibers incorporated with IGF growth factor has strong effect on PDL fibroblasts, mitogenesis, and protein synthesis which promotes osteogenesis and cementogenesis. A patient having grade II furcation and intrabony defect was treated and evaluated after 12 months with biodegradable fibers infused with insulin like growth factor and bio oss xeno graft irt 36. Treated site responded well to the use of the bovine bone mineral with good tissue response and an improvement and there was an overall mean probing pocket reduction in the deepest site of osseous defects. The clinical parameters assessed are plaque index, bleeding on brobing, pocket probing depth, clinical attachment level, glickman’s furcation index and RVG at baseline, 6 and 12 months post operatively. Both the bone grafts resulted in better regeneration when compared to base line and 12 months.Bio oss (bovine bone mineral) and biodegradable fibres infused with insulin like growth factor materials are of considerable promise for regeneration with better clinical and radiographic outcomes.

Assessing Genotoxicity of Bovine Pericardium in Guided Tissue Regeneration: Bacterial Reverse Mutation Assay With Exogenous Metabolic Activation.

Introduction Guided tissue regeneration (GTR) is integral to periodontal therapy, facilitating the repair of osseous defects. Due to the widespread use of bovine pericardium (BP) in GTR, a thorough investigation into its genotoxicity is essential for patient safety and treatment efficacy. This study aimed to evaluate the genotoxic effects of local BP in GTR for periodontal osseous defects. Materials and methods The Bacterial Reverse Mutation Assay (Ames test) was used to assess the genotoxic potential of local BP. An exogenous metabolic activation system was employed to evaluate the direct effects of the material on bacterial cells. Results The study investigated the mutagenic effects of local BP across multiple strains of Salmonella typhimurium, utilizing concentrations ranging from 0.3125 mg/plate to 5 mg/plate. While some variability was observed in revertant counts, the generally low SDs suggest a consistent response to the test substance. The maximum revertant count for each strain did not significantly exceed the mean values, indicating the absence of notable outliers or exceptionally high revertant counts at any specific concentration. Based on the data and toxicity assessment criteria, there is insufficient evidence to suggest that the experimental material induces genotoxic effects in the tested bacterial strains under the provided experimental conditions. Conclusion This study assessed the mutagenic potential of local BP membranes used in GTR with the Ames test. Results showed no evidence of mutagenicity, as revertant counts did not exceed twice the negative control in all bacterial strains with exogenous metabolic activation. This suggests that bovine pericardium membranes are safe for medical use under the test conditions. The study highlights the biocompatibility and non-mutagenic nature of BP membranes in GTR for periodontal therapy.

Spontaneous Intraventricular Tension Pneumocephalus

Here, we report a very rare case of spontaneous intraventricular tension pneumocephalus. This case concerns a 40-year-old patient with medical history of a tumor of the pineal region and a secondary hydrocephalus treated by multiple ventriculoperitoneal shunts. He presented in the emergency room because of unusual headaches, nausea, and visual loss. In addition, he reported slight rhinorrhea in the past few weeks. The initial brain computed tomography scan revealed a spontaneous intraventricular tension pneumocephalus. There was no history of recent head trauma and no sign of disconnection of the shunt system. A complementary radiologic assessment including a thin-slice bone computed tomography scan and a radioisotope cisternography revealed an osseous defect and an isotope leakage at the junction between the tegmen tympani and the squamous part of the left temporal bone. A middle cranial fossa surgery was performed to repair the osteo-meningeal breach.

Upper Extremity Diaphyseal Osseous Gap Reconstruction with Free Vascularized Bone Flaps: A Scoping Review.

Reconstruction of upper extremity osseous diaphyseal defects often requires complex reconstructions. In this study, we characterized and summarized the available literature on free vascularized bone flap (VBF) reconstruction for upper extremity diaphyseal defects. A scoping review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis extension for Scoping Reviews was conducted. A literature search of major electronic databases was conducted to identify journal articles relating to the management of VBF reconstruction of upper limb long bone defects. Articles with patient-level data were included. Descriptive statistics were performed using Python. Overall, 364 patients were included in this study. The most common indications for VBFs included atrophic nonunion (125, 34.3%), postoncologic resection (125, 34.3%), septic nonunion (56, 15.4%), and trauma (36, 9.9%). Mean defect size was 8.53 ± 5.14 cm. A total of 67 (18.4%) cases had defects < 6 cm, and 166 cases (45.6%) had defects > 6 cm. The fibula was the most utilized VBF (272, 74.73%), followed by the medial femoral condyle flap (69, 18.96%). Overall, primary union rate was 87.1%. Subsequent flap fracture rate was 3.3%. There were only two (0.6%) VBF losses reported in the included cases, and donor-site complications were similarly rare (17, 4.7%). VBF reconstruction is often utilized for postoncologic defects and recalcitrant nonunions. The fibula is the most utilized VBF, but the medial femoral condyle flap is used frequently for smaller defects. VBF reconstruction demonstrates high union rates and low flap fracture rate across indications.

The effect of autologous demineralized dentin matrix on postoperative complications and wound healing following lower third molar surgery: A split-mouth randomized clinical trial

Background/purposeAutologous dentin materials are among the most promising bone substitutes for preventing osseous defects on the distal side of the lower second molar. This study aimed to investigate the effects of autologous demineralized dentin matrix on postoperative complications and wound healing after lower third molar surgery. Materials and methodsThirteen patients with bilateral symmetrical lower third molars participated in this split-mouth randomized clinical trial. After removal surgery, one socket of the lower third molar was grafted with dentin material (demineralized dentin matrix side), and a piece of collagen sponge was used for the tooth socket of the remaining side (control side). The upper third molar on the same lateral side was extracted immediately before lower third molar surgery and used to create a demineralized dentin matrix according to the manufacturer's protocol (KometaBio). After lower third molar surgery, pain, swelling, trismus, and Inflammatory Proliferative Remodeling Scale scores were used to evaluate postoperative complications and wound healing. ResultsPain, swelling, and trismus of the demineralized dentin matrix and control sides were not significantly different at any assessment time (P > 0.05). The wound-healing scores of the demineralized dentin matrix side were better than those of the control side; however, the differences were only significant at 7th and 30th days (P < 0.05). ConclusionGrafting autologous demineralized dentin matrix into the tooth socket did not increase the postoperative complications after lower third molar surgery. However, wound healing on the graft side was comparatively better than that on the control side. Clinicaltrials.gov identifierNCT06073639, date 10 October, 2023. This is a retrospectively registered trial.

Periodontal granulation tissue - To remove or not to remove, that is the question.

Formation of granulation tissue is a fundamental phase in periodontal wound healing with subsequent maturation leading to regeneration or repair. However, persistently inflamed granulation tissue presents in osseous defects as a result of periodontitis and is routinely disrupted and discarded with non-surgical and surgical therapy to facilitate wound healing or improve chances of regeneration. Histological assessment suggests that granulation tissue from periodontitis-affected sites is effectively a chronic inflammatory tissue resulting from impaired wound healing due to persistence of bacterial dysbiotic bioflim. Nevertheless, the immunomodulatory potential and stem cell characteristics in granulation tissue have also raised speculation about the tissue's regenerative potential. This has led to the conception and recent implementation of surgical techniques which preserve granulation tissue with the intention of enhancing innate regenerative potential and improve clinical outcomes. As knowledge of fundamental cellular and molecular functions regulating periodontitis-affected granulation tissue is still scarce, this review aimed to provide a summary of current understanding of granulation tissue in the context of periodontal wound healing. This may provide new insights into clinical practice related to the management of granulation tissue and stimulate further investigation.

The effects of keratin-coated titanium on osteoblast function and bone regeneration

Wool derived keratin, due to its demonstrated ability to promote bone formation, has been suggested as a potential bioactive material for implant surfaces. The aim of this study was to assess the effects of keratin-coated titanium on osteoblast function in vitro and bone healing in vivo. Keratin-coated titanium surfaces were fabricated via solvent casting and molecular grafting. The effect of these surfaces on the attachment, osteogenic gene, and osteogenic protein expression of MG-63 osteoblast-like cells were quantified in vitro. The effect of these keratin-modified surfaces on bone healing over three weeks using an intraosseous calvaria defect was assessed in rodents. Keratin coating did not affect MG-63 proliferation or viability, but enhanced osteopontin, osteocalcin and bone morphogenetic expression in vitro. Histological analysis of recovered calvaria specimens showed osseous defects covered with keratin-coated titanium had a higher percentage of new bone area two weeks after implantation compared to that in defects covered with titanium alone. The keratin-coated surfaces were biocompatible and stimulated osteogenic expression in adherent MG-63 osteoblasts. Furthermore, a pilot preclinical study in rodents suggested keratin may stimulate earlier intraosseous calvaria bone healing.

Treatment of an Infrabony Defect of a Maxillary Canine Tooth Using Enamel Matrix Derivatives with Allogeneic Bone Augmentation in a Dog.

A 5-year-old Miniature Dachshund was presented having an infrabony pocket on the palatal aspect of the right maxillary canine tooth. The bony defect had worsened despite previous closed root planing and administration of a perioceutic agent. A second surgery using an allogeneic cancellous bone augmentation with an enamel matrix derivative was performed in the infrabony defect following open root planing. Eight months after the periodontal surgery, the osseous defect showed healing by improved periodontal probing measurements and increased radiopacity using dental radiography and computed tomography.

Characterization of patient population receiving bioactive glass bone graft substitute as intraoperative treatment for orthopaedic trauma fractures

BackgroundBioactive glass synthetic bone grafts are used to treat osseous defects in orthopaedic surgery. Characterization of the clinical scenarios associated with bioactive glass use in the context of orthopaedic trauma, are not well established. This study aims to characterize population demographics, operative variables, as well as postoperative variables, for patients who required bone grafting for treatment of traumatic orthopaedic injuries and received a bioactive glass bone substitute intraoperatively. MethodsThe electronic medical record at a large Level I trauma center was queried for fracture patients between January 1st, 2019, and April 30th, 2022. Our retrospective cohort included fracture patients who received Fibergraft Matrix or Fibergraft Putty intraoperatively, and their respective control groups. This study ascertained patient demographic variables, operative variables, and postoperative variables. Differences in categorical variables were tested with Fischer's Exact Tests, while differences in continuous variables were tested with ANOVA. Statistical significance was determined as P < 0.05. If the overall Group model was significant for a given variable, post-hoc Fischer's Exact or Tukey HSD tests were used to assess pairwise significance between individual Group pairs. ResultsA total of four categories across our analysis of demographic, operative, and postoperative variables displayed significant differences amongst subject Groups (P ≤ 0.03). Individual groups were compared such that significant differences between subject groups could be appreciated for a specific variable. FM subjects had greater length of surgery, billable costs, and vitamin D supplementation at the time of surgery compared to FM controls. Similarly, FP subjects had greater length of surgery, billable cost, and implants used intraoperatively compared to FP controls. ConclusionThis analysis revealed Fibergraft patients to have greater length of surgery and billable cost, with respect to their matched controls. These data suggest that Fibergraft patients had more severe orthopaedic fractures compared to matched controls.

Shape variation and sex differences of the adult human mandible evaluated by geometric morphometrics

In cases of osseous defects, knowledge of the anatomy, and its age and sex-related variations, is essential for reconstruction of normal morphology. Here, we aimed at creating a 3D atlas of the human mandible in an adult sample using dense landmarking and geometric morphometrics. We segmented 50 male and 50 female mandibular surfaces from CBCT images (age range: 18.9–73.7 years). Nine fixed landmarks and 510 sliding semilandmarks were digitized on the mandibular surface, and then slid by minimizing bending energy against the average shape. Principal component analysis extracted the main patterns of shape variation. Sexes were compared with permutation tests and allometry was assessed by regressing on the log of the centroid size. Almost 49 percent of shape variation was described by the first three principal components. Shape variation was related to width, height and length proportions, variation of the angle between ramus and corpus, height of the coronoid process and inclination of the symphysis. Significant sex differences were detected, both in size and shape. Males were larger than females, had a higher ramus, more pronounced gonial angle, larger inter-gonial width, and more distinct antegonial notch. Accuracy of sexing based on the first two principal components in form space was 91 percent. The degree of edentulism was weakly related to mandibular shape. Age effects were not significant. The resulting atlas provides a dense description of mandibular form that can be used clinically as a guide for planning surgical reconstruction.

Periodontal Osseous Defect Management Modalities: A Literature Review

Periodontal Osseous Defect Management Modalities: A Literature Review

275 Absence of Hindbrain Herniation in Myelomeningocele Myeloschisis: A Closer Look at Patients Who Progress to Hindbrain Herniation in the Prenatal and Postnatal Period

INTRODUCTION: Prenatal repair is the gold standard for appropriate patients with fetal myelomeningocele/myeloschisis. Hindbrain herniation is a prerequisite for fetal repair; however, there is a subset of patients without herniation on initial imaging and then progress to herniation on subsequent prenatal/postnatal imaging. METHODS: From July 2016 to July 2022, patients seen at the Center of Fetal Diagnosis and Treatment for myelomeningocele/myeloschisis were evaluated for hindbrain herniation. The osseous lesion level was defined as the bony defect level on prenatal ultrasound. Prenatal sac volume was measured on MRI. Prenatal ventricular size was determined on US. The fronto-occipital horn ratio was measured on the first postnatal US. RESULTS: Of 422 patients identified with a prenatal diagnosis of myelomeningocele/myeloschisis, 73 were identified who initially had negative hindbrain herniation; of these, 9 and 11 patients progressed to herniation on subsequent prenatal and postnatal imaging, respectively; 32 remained without herniation throughout the prenatal/postnatal period. Sac volume was significant (p = 0.04) for those whose hindbrain herniation was detected on subsequent prenatal visits but not for those diagnosed in the postnatal period (p = 0.10). The majority of patients with hindbrain herniation progression had L1-2 lesions. A subset of patients ultimately underwent permanent CSF diversion (no herniation: 21.8%, prenatal herniation: 33.3%, postnatal herniation: 36.3%). CONCLUSIONS: Patients who initially exhibit no hindbrain herniation and then ultimately progress to herniation in subsequent prenatal or postnatal evaluation are more likely to have higher levels of osseous defect. Sac volume was determined as significant for delayed prenatal progression of hindbrain herniation. Further long-term outcomes are necessary to better characterize this unique cohort of patients.