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The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1–18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity.

To explore the role of YAP, a key effector of the Hippo pathway, in temporomandibular joint (TMJ) ankylosis. The temporal and spatial expression of YAP was detected via immunohistochemistry and multiplex immunohistochemistry on postoperative Days 1, 4, 7, 9, 11, 14 and 28 in a sheep model. Isolated mesenchymal stem cells (MSCs) from samples of the Day 14. The relative mRNA expression of YAP was examined before and after the osteogenic induction of MSCs. A YAP-silenced MSC model was constructed, and the effect of YAP knockdown on MSC function was examined. YAP is expressed in the nucleus of the key sites that determine the ankylosis formation, indicating that YAP is activated in a physiological state. The expression of YAP increased gradually over time. Moreover, the number of cells coexpressing of RUNX2 and YAP—with the osteogenic active zone labelled by RUNX2—tended to increase after Day 9. After the osteogenic induction of MSCs, the expression of YAP increased. After silencing YAP, the osteogenic, proliferative and migratory abilities of the MSCs were inhibited. YAP is involved in the early development of TMJ bony ankylosis. Inhibition of YAP using shRNA might be a promising way to prevent or treat TMJ ankylosis.

This study aimed to describe the clinical features of different types of traumatic temporomandibular joint (TMJ) ankylosis. Seventy-one patients with 102 ankylosed joints were retrospectively reviewed and categorized into four groups according to the grades of severity: type I, non-bony ankylosis of the joint with almost-normal joint space; type II, lateral bony ankylosis marked by a normal joint space that coexists with a radiolucent line; type III, complete bony ankylosis of the joint characterized by only a radiolucent line; and type IV, extensive bony ankylosis without any radiolucent line. The period of ankylosis, maximal mouth opening (MMO), rate of complications, and histopathological changes were compared among groups. Intergroup comparison showed significant differences in the clinical features of MMO and the incidence of complications (p < 0.05). Younger trauma patients tended to develop more severe types of ankylosis than older patients. Additionally, long post-trauma periods were related to the development of severe ankylosis. MMO was highly negatively correlated with the severity of ankylosis. Significant differences were noted among the four types of ankylosis. Younger trauma patients with long post-trauma periods tended to develop more severe TMJ ankylosis, experience more complications, and face more challenges in treatment than older patients.

Tooth ankylosis is a pathological condition of periodontal ligament (PDL) restoration after tooth replantation. Platelet-derived growth factor-BB (PDGF-BB) has been proposed as a promising factor for preventing tooth ankylosis. Using rat tooth replantation model, we investigated whether PDGF-BB accelerates the repair of PDL after tooth replantation without ankylosis, and its molecular mechanisms. In PDGF-BB pretreated replanted teeth (PDGF-BB group), ankylosis was markedly reduced and functionally organized PDL collagen fibers were restored; the mechanical strength of the healing PDL was restored to an average of 76% of that in non-replanted normal teeth at 21 days. The numbers of PDGF-Rβ- and BrdU-positive cells in the periodontal tissues of the PDGF-BB group were greater than those of atelocollagen pretreated replanted teeth (AC group). Moreover, in the PDGF-BB group, the periodontal tissues had fewer osteocalcin-positive cells and decreased number of nuclear β-catenin-positive cells compared to those in the AC group. In vitro analyses showed that PDGF-BB increased the proliferation and migration of human periodontal fibroblasts. PDGF-BB downregulated mRNA expressions of RUNX2 and ALP, and inhibited upregulatory effects of Wnt3a on β-catenin, AXIN2, RUNX2, COL1A1, and ALP mRNA expressions. These findings indicate that in tooth replantation, topical PDGF-BB treatment enhances cell proliferation and migration, and inhibits canonical Wnt signaling activation in bone-tooth ankylosis, leading to occlusal loading of the PDL tissues and subsequent functional restoration of the healing PDL. This suggests a possible clinical application of PDGF-BB to reduce ankylosis after tooth replantation and promote proper regeneration of PDL.

Background The psychological symptoms of temporomandibular joint (TMJ) ankylosis were similar to that of depressive disorder, but there were no relevant evidences to confirm that the humans or animals with TMJ ankylosis had depressive disorder. The aim of this study was to investigate the association between TMJ ankylosis and depressive disorder in the rat model. Methods Thirty 3-week-old male Sprague–Dawley (SD) rats were used in this study. The damage of TMJ complexes and narrowed joint space were performed in the unilateral TMJ of test group to induce TMJ bony ankylosis (experimental side). The other TMJ of test group underwent a sham operation (sham side). The TMJs of control group did not undergo any operations. At 8 weeks postoperatively, behavioral tests, body weight, passive maximum mouth opening (PMMO), and TMJ morphological features were evaluated, and the hippocampuses were analyzed using western blotting and immunocytochemistry. The data was compared between the test group and control group by independent t-test, between the experimental side and sham side by paired t-test. The correlations between PMMO/area of bony fusion and duration of immobility, sucrose preference, CB1 receptor protein, mean optical density of CB1 receptor protein, and the number of BrdU-positive cell were evaluated using linear regression analysis. The level of significance was 0.05. Results In the test group, the traumatic TMJ complexes with narrowed joint space developed TMJ bony ankylosis, the area of bony mass of experimental side (21.26 mm 2 ) was larger than that of sham side (1.73 mm 2 ) ( p  < 0.001). There were significant difference with the sucrose preference (test group: 0.36, control group: 0.76, p  < 0.001), duration of immobility (test group: 127.36 s, control group: 59.41 s, p  < 0.001), body weight (test group: 156.70 g, control group: 270.06 g,  p  < 0.001), PMMO (test group: 9.98 mm, control group: 28.79 mm, p  < 0.001), CB1 receptor protein (test group: 41.00%, control group: 86.69%, p  < 0.001), mean optical density of CB1 receptor protein (test group: 29.60 a.u., control group: 54.69 a.u., p  < 0.001), and the number of BrdU-positive cell between the test group and control group (test group: 2133.71, control group: 4301.95, p  < 0.001). PMMO was negatively correlated with the duration of immobility ( r = 0.953, p  < 0.001), while the area of bony fusion was positively correlated (r = 0.961, p  < 0.001). PMMO was positively correlated with the sucrose preference, CB1 receptor protein, mean optical density of CB1 receptor protein, and the number of BrdU-positive cell ( r = 0.955, 0.955, 0.976, 0.958, p  < 0.001, all), while the area of bony fusion was negatively correlated ( r = 0.970, 0.981, 0.971, 0.958, p  < 0.001, all). Conclusions The present study verified that depressive disorder was found in the rat model of traumatic TMJ bony ankylosis. The severity of TMJ bony ankylosis correlated with the severity of depressive disorder.

Objectives To evaluate the feasibility and diagnostic accuracy of a deep learning network for detection of structural lesions of sacroiliitis on multicentre pelvic CT scans. Methods Pelvic CT scans of 145 patients (81 female, 121 Ghent University/24 Alberta University, 18–87 years old, mean 40 ± 13 years, 2005–2021) with a clinical suspicion of sacroiliitis were retrospectively included. After manual sacroiliac joint (SIJ) segmentation and structural lesion annotation, a U-Net for SIJ segmentation and two separate convolutional neural networks (CNN) for erosion and ankylosis detection were trained. In-training validation and tenfold validation testing (U-Net— n  = 10 × 58; CNN— n  = 10 × 29) on a test dataset were performed to assess performance on a slice-by-slice and patient level (dice coefficient/accuracy/sensitivity/specificity/positive and negative predictive value/ROC AUC). Patient-level optimisation was applied to increase the performance regarding predefined statistical metrics. Gradient-weighted class activation mapping (Grad-CAM++) heatmap explainability analysis highlighted image parts with statistically important regions for algorithmic decisions. Results Regarding SIJ segmentation, a dice coefficient of 0.75 was obtained in the test dataset. For slice-by-slice structural lesion detection, a sensitivity/specificity/ROC AUC of 95%/89%/0.92 and 93%/91%/0.91 were obtained in the test dataset for erosion and ankylosis detection, respectively. For patient-level lesion detection after pipeline optimisation for predefined statistical metrics, a sensitivity/specificity of 95%/85% and 82%/97% were obtained for erosion and ankylosis detection, respectively. Grad-CAM++  explainability analysis highlighted cortical edges as focus for pipeline decisions. Conclusions An optimised deep learning pipeline, including an explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical performance on a slice-by-slice and patient level. Clinical relevance statement An optimised deep learning pipeline, including a robust explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical metrics on a slice-by-slice and patient level. Key Points • Structural lesions of sacroiliitis can be detected automatically in pelvic CT scans. • Both automatic segmentation and disease detection yield excellent statistical outcome metrics. • The algorithm takes decisions based on cortical edges, rendering an explainable solution.

Background Heterotopic ossification is the most common extrinsic cause of elbow contracture and may lead to clinically important stiffness, and rarely, complete bony ankylosis. Surgery sometimes is performed to treat this problem, and published reports differ regarding the factors that are associated with success or failure after this operation and whether the procedure is effective for patients with elbow ankylosis. Questions/purposes We wished (1) to identify potential patient characteristics and modifiable risk factors that are associated with improvements in ROM after surgery for heterotopic ossification of the elbow; (2) to compare ROM gains between patients with complete ankylosis and partially restricted ROM; and (3) to characterize the complications of elbows treated by surgical release and excision of heterotopic ossification followed by a standardized rehabilitation program. Methods We reviewed the records of all patients treated operatively for heterotopic ossification of the elbow from September 1999 to February 2012 at one institution by one surgeon. General indications for the surgery were clinically symptomatic or debilitating heterotopic ossification of the elbow. Each patient received prophylaxis postoperatively consisting of indomethacin (or single-shot radiation for patients with sensitivity to antiinflammatory medications). All patients received a physical therapy regimen and used a continuous passive motion machine for 6 weeks. Patient demographics, mechanism of injury, time between injury and surgery, and medical history were reviewed for comparison. Followup was at a mean of 13 months (range, 3–106 months); no patients were lost to followup. Thirty-nine patients (46 elbows) with heterotopic ossification treated with excision were identified: 10 patients (16 elbows) had burns, 28 patients (29 elbows) had trauma, and one patient (one elbow) had a closed head injury. Eight of the 39 patients (12 of 46 elbows [26%]) had complete ankylosis at the time of surgery. Results Hypertension, obesity, and absence of intraoperative anterior ulnar nerve transposition were associated with an adverse effect on change from preoperative to final arc of motion. The group with ankylosis had greater preoperative to postoperative gain in arc compared with the group with partial restriction (96°, 95% CI, 84°–107° and 59°, 95% CI, 46°–72°, respectively). For the entire cohort there was an overall improvement in mean flexion-extension arc of motion from 35° to 103° at final followup (p < 0.001; 95% CI, 57°–80°), with a 17% rate of complications (three patients [three elbows] with heterotopic ossification, three patients [three elbows] with nerve palsies, one patient [one elbow] with deep wound infection, and one patient [one elbow] with an unstable elbow). Conclusions Patients with partially and completely restricted ROM showed substantial improvement in postoperative ROM. Hypertension, obesity, and absence of intraoperative anterior ulnar nerve transposition were negative predictors of outcome in our series. Surgery combined with postoperative prophylaxis and a regimented rehabilitation program are feasible modalities to treat patients with heterotopic ossification of the elbow. Level of Evidence Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Background This study reports the mid-term outcomes of primary total hip arthroplasty (THA) and investigates the effect of bony ankylosis on postoperative hip function in patients with ankylosing spondylitis (AS). Methods We identified 544 primary THAs performed in 319 consecutive patients with AS (median age, 33 years) from 2012 to 2017. Survivorship of the implants, complications, and patient satisfaction were investigated. Functional outcomes were assessed by the measurement of hip flexion–extension range of motion (ROM), the Harris hip score (HHS), and the Western Ontario and McMaster Universities Arthritis Index (WOMAC). The hips undergoing THA were divided into a bony ankylosis group and a hip stiffness group based on the severity of hip involvement. The postoperative functional results of the two groups at the most recent follow-up were compared. Results Survivorship was 99.8% with a mean follow-up of 7 years (range, 5–9 years). The main complications included dislocation (5 hips, 0.9%), periprosthetic femoral fracture (15 hips, 2.7%), and infection (primary infection in 2 hips and periprosthetic joint infection in 1 hip, 0.6%). The flexion–extension ROM improved significantly with a median of 0° (0 ~ 120°) pre-operatively to 100° (30 ~ 130°) after THA ( P  < 0.001), and the HHS improved from 37 ± 19 to 90 ± 5 ( P  < 0.001). Patient satisfaction was self-scored as ‘Very satisfied’ in 278 (87%) of patients. The most common cause of dissatisfaction in the remaining 41 (13%) patients was poor hip flexion function (58.5% of this subset). Postoperative ROM was significantly lower in the bony ankylosis hips (median, 100° bony ankylosis group vs. 110° hip stiffness group). The bony ankylosis group also had lower postoperative HHS (89 ± 5 vs. 92 ± 5) and had significantly higher WOMAC scores (43 ± 20 vs. 31 ± 18) than the hip stiffness group ( P  < 0.001). Conclusions Excellent mid-term clinical outcomes can be achieved with modern cementless THA in patients with AS. Poor hip flexion function is the main complaint of patients who are dissatisfied with their outcomes. Bony ankylosis has adverse effects on postoperative hip function in patients with AS, suggesting that performing THA before ankylosis occurs can lead to better subjective outcomes and better postoperative hip function. Level of evidence Level III.

Temporomandibular joint (TMJ) ankylosis is a refractory disease that is difficult to predictably treat. This study evaluated the prognosis of using standard alloplastic TMJ prostheses for the treatment of TMJ ankylosis in Chinese patients with severe mandibular deficiency. Patients treated from 2013 to 2015 were reviewed. The computer-aided design and manufacture (CAD/CAM) technique was used to guide bony mass removal and locate the TMJ prosthesis (Biomet, USA). Eleven patients were included in this study. All prostheses were successfully installed and stabilized intraoperatively. In 4 patients with severe mandibular deficiency, their mandibular ramus was elongated by the TMJ prosthesis and 2 patients were combined with Le Fort I osteotomy guided by digital templates. Their mean chin advancement was 10.19 mm. Their SNB and ramus heights were also significantly improved after operation (P < 0.05). There was no prosthesis loosening, breakage, or infection leading to removal after a mean follow-up period of 22 months (range, 12-31mos.). Mouth opening was significantly improved from 5.5 mm preoperatively to 31.5 mm postoperatively. TMJ reconstruction with standard alloplastic prosthesis is a reliable treatment for ankylosis, especially in recurrent cases. By CAD/CAM technique, it can correct jaw deformities simultaneously and produce stable results.

Paget’s disease is a condition marked by abnormal bone remodeling, involving both excessive bone formation and destruction, predominantly in the elderly. Pagetic vertebral ankylosis is a rare manifestation, often associated with Paget’s disease, ankylosing spondylitis, or diffuse idiopathic skeletal hyperostosis. This form of acquired vertebral ankylosis is uncommon and occurs in cases with bone-bridging syndesmophytes or osteophytes. Here, we present a case of delayed diagnosis of Paget’s disease in the lower vertebral column, progressing to cervicothoracic vertebral ankylosis secondary to ankylosing spondylitis.