Cholesteatoma Severely Impacts the Integrity and Bone Material Quality of the Incus.

Cholesteatoma can lead to progressive destruction of the auditory ossicles along with conductive hearing loss but precise data on the microstructural, cellular, and compositional aspects of affected ossicles are not available. Here, we obtained incus specimens from patients who had cholesteatoma with conductive hearing loss. Incudes were evaluated by micro-computed tomography, histomorphometry on undecalcified sections, quantitative backscattered electron imaging, and nanoindentation. Results were compared with two control groups taken from patients with chronic otitis media as well as from skeletally intact donors at autopsy. The porosity of incus specimens was higher in cholesteatoma than in chronic otitis media, along with a higher osteoclast surface per bone surface. Histomorphometric assessment revealed higher osteoid levels and osteocyte numbers in cholesteatoma incudes. Incudes affected by cholesteatoma also showed lower matrix mineralization compared with specimens from healthy controls and chronic otitis media. Furthermore, the modulus-to-hardness ratio was higher in cholesteatoma specimens compared with controls. Taken together, we demonstrated increased porosity along with increased osteoclast indices, impaired matrix mineralization, and altered biomechanical properties as distinct features of the incus in cholesteatoma. Based on our findings, a possible impact of impaired bone quality on conductive hearing loss should be further explored.

Radiolucent zones of biodegradable magnesium-based screws in children and adolescents-a radiographic analysis.

INTRODUCTION: Albeit the implantation of magnesium-based biodegradable implants can avoid a second surgery for implant removal, the postoperative occurrence of radiolucent zones around these implants based on corrosion processes has not been previously investigated in children and adolescents. We sought to characterize the distinct temporal and spatial dynamics for magnesium-based implants based on standard clinical routine radiographs. MATERIALS AND METHODS: We retrospectively analyzed 29 patients, treated with magnesium-based compression screws (MAGNEZIX® CS 2.7 mm, CS 3.2 mm, CSC 4.8 mm; Syntellix AG) for fracture fixation, osteotomy, or osteochondral refixation. During a follow-up examination, the clinical and functional status was evaluated. Based on digital radiographs, the ratio of the area of the radiolucent zone and that of the screw was evaluated to assess implant degradation at two follow-up visits (i.e., after 6-8 weeks and 12-24 weeks). RESULTS: In 29 patients (16/29 females, 14.03 ± 2.13 years), a total of 57 implants were evaluated that were used for osteotomy (n = 13, screws n = 26), fracture fixation (n = 9, screws n = 18), or osteochondral refixation (n = 7, screws n = 13). All patients healed without complications and regained full function. Radiolucent zones were observed in 27/29 patients at the first follow-up, with significantly decreased ratios at the second follow-up (2.10 ± 0.55 vs 1.64 ± 0.60, p = 0.0006). Regression analyses were performed to assess the temporal dynamics of radiolucent zones and revealed significant logarithmic developments for the 2.7 mm and 3.2 mm screws, marked by a strong ratio decrease during the first weeks and an almost complete disappearance after approximately 100 days and 200 days, respectively. In contrast, the ceramic-coated 4.8 mm screws presented a significant linear and slower decrease of radiolucent zones. CONCLUSION: Radiolucent zones are a common phenomenon in the course of implant degradation. However, they represent a self-limiting phenomenon. Remarkably, neither implant failure nor affected implant function is noted in this context. Yet, the microstructural changes accompanying the presence of radiolucent zones remain to be analyzed by three-dimensional high-resolution imaging.

Impaired Bone Microarchitecture at Distal Radial and Tibial Reference Locations Is Not Related to Injury Site in Athletes With Bone Stress Injury.

BACKGROUND: Bone stress injuries (BSIs) are common sports injuries that occur because of an imbalance between microdamage accumulation and removal through bone remodeling. The underlying bone phenotype has been assumed to be a contributing factor. However, the bone microarchitecture of athletes with BSI is not well characterized, and no study has investigated whether impaired bone microarchitecture is associated with bone composition or anatomic site of injury. PURPOSE/HYPOTHESIS: This cross-sectional study characterizes the bone microarchitecture at distal radial and tibial reference locations in athletes with BSI. Based on previous dual-energy X-ray absorptiometry (DXA) findings, the aim was to compare anatomic injury sites, hypothesizing that athletes with BSIs in bones with greater trabecular composition show impaired bone microarchitecture parameters compared with those with BSIs in bones with greater cortical composition. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Athletes who had presented to our outpatient clinic because of a high-grade BSI (ie, stress fracture) were retrospectively included. Blood and urine samples were collected. Areal bone mineral density (aBMD) was assessed by DXA at the lumbar spine and both hips. Bone microarchitecture was analyzed by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and tibia. HR-pQCT parameters were expressed in relation to available sex-, age-, and device-adjusted reference values and compared with a cohort of 53 age- and sex-matched controls. RESULTS: In total, 53 athletes had a BSI of the foot (n = 20), tibia/fibula (n = 18), pelvis (n = 9), femur (n = 5), or sternum (n = 1). Based on DXA measurements, a Z-score of -1.0 or lower was found in 32 of 53 (60.4%) of the athletes, of whom 16 of 53 (30.2%) had a Z score -2.0 or lower. While an impairment of cortical area (P = .034 and P = .001) and thickness (P = .029 and P < .001) was detected at the distal radius and tibia in the BSI cohort compared with controls, no differences in BMD or bone microarchitecture were observed between anatomic injury sites. Furthermore, no difference was revealed when BSIs were grouped into cortical- and trabecular-rich sites. CONCLUSION: Reduced aBMD and impaired cortical bone microarchitecture were present in a considerable number of athletes with BSI. Neither aBMD nor bone microarchitecture was related to the injury site, highlighting the multifactorial etiology of BSI.

Prevention of Hypomineralization In Auditory Ossicles of Vitamin D Receptor (Vdr) Deficient Mice.

Intact mineralization of the auditory ossicles - the smallest bones in the body - is essential for sound transmission in the middle ear, while ossicular hypomineralization is associated with conductive hearing loss. Here, we performed a high-resolution analysis of the ossicles in vitamin D receptor deficient mice (Vdr-/- ), which are characterized by hypocalcemia and skeletal mineralization defects, and investigated whether local hypomineralization can be prevented by feeding a calcium-rich rescue diet (Vdr-/- res ). In Vdr-/- mice fed a regular diet (Vdr-/- reg ), quantitative backscattered electron imaging (qBEI) revealed an increased void volume (porosity, p<0.0001) along with lower mean calcium content (CaMean, p=0.0008) and higher heterogeneity of mineralization (CaWidth, p=0.003) compared to WT mice. Furthermore, a higher osteoid volume per bone volume (OV/BV; p=0.0002) and a higher osteocyte lacunar area (Lc.Ar; p=0.01) were found in histomorphometric analysis in Vdr-/- reg mice. In Vdr-/- res mice, full rescue of OV/BV and Lc.Ar (both p>0.05 vs. WT) and partial rescue of porosity and CaWidth (p=0.02 and p=0.04 vs. WT) were observed. Compared with Hyp mice, a model of X-linked hypophosphatemic rickets, Vdr-/- reg mice showed a lower osteoid volume in the ossicles (p=0.0002), but similar values in the lumbar spine. These results are consistent with later postnatal impairment of mineral homeostasis in Vdr-/- mice than in Hyp mice, underscoring the importance of intact mineral homeostasis for ossicle mineralization during development. In conclusion, we revealed a distinct phenotype of hypomineralization in the auditory ossicles of Vdr-/- mice that can be partially prevented by a rescue diet. Since a positive effect of a calcium-rich diet on ossicular mineralization was demonstrated, our results open new treatment strategies for conductive hearing loss. Future studies should investigate the impact of improved ossicular mineralization on hearing function.

Investigation of distal femur microarchitecture and factors influencing its deterioration: An ex vivo high-resolution peripheral quantitative computed tomography study.

While fractures of the distal femur are often considered as fragility fractures, detailed knowledge of the bone microarchitecture at this skeletal site is largely unavailable. Initial evaluation of a patient cohort with distal femur fractures showed a markedly increased occurrence in elderly women. The purpose of this study was to determine the extent to which demographic characteristics of distal femur fractures are reflected by general age- and sex-specific variations in local microarchitectural parameters. Fifty cadaveric femora were collected from 25 subjects (12 females, 13 males, age 25-97 years). A volume of interest within 3 cm proximal to the condyles was analyzed using high-resolution peripheral quantitative computed tomography (HR-pQCT), which revealed impaired trabecular and cortical bone microarchitecture in women compared to men as well as in osteoporotic compared to normal or osteopenic subjects, as classified by dual-energy X-ray absorptiometry (DXA) T-score. Linear regression analyzes showed negative associations between age and HR-pQCT parameters in women (e.g., cortical thickness -14 µm/year, 95% CI: -21 to -7 µm/year), but not in men (e.g., cortical thickness 1 µm/year, 95% CI: -12 to 14 µm/year). HR-pQCT parameters showed strong positive associations with areal bone mineral density (aBMD) determined by DXA at the hip in both sexes. Taken together, our findings suggest that female sex, advanced age, and low aBMD represent major risk factors for impaired microarchitecture at the distal femur. Both the diagnostic value of DXA for predicting distal femur fractures and the efficacy of bone-specific agents on fracture risk reduction should be investigated in the future.

Prevalence of osteoporosis and osteopenia in elderly patients scheduled for total knee arthroplasty.

INTRODUCTION: Osteoporosis is a common comorbidity in elderly patients with osteoarthritis (OA) and may increase perioperative complications in orthopedic surgery (e.g., component migration, periprosthetic fractures). As there is no investigation of bone mineral density (BMD) in elderly patients prior to total knee arthroplasty (TKA) in Europe, we investigated this issue with a particular focus on a potential treatment gap. MATERIALS AND METHODS: We assessed the BMD by dual-energy X-ray absorptiometry (DXA) in 109 consecutive elderly patients (age ≥ 70 years) scheduled for TKA. In addition to a detailed assessment of osteoporosis and osteopenia, the influence of clinical risk factors and radiological OA severity on BMD was evaluated using group comparisons and linear regression models. In addition, we analyzed differences in BMD between patients scheduled for TKA vs. total hip arthroplasty (THA). RESULTS: Of the included 109 patients, 19 patients (17.4%) were diagnosed with osteoporosis and 50 (45.9%) with osteopenia. In the osteoporotic patients, a clinically relevant underdiagnosis concomitant with a serious treatment gap was observed in 95.0% of the patients. Body mass index, OA grade, and glucocorticoid use were identified as independent factors associated with BMD. No differences in BMD were found between the patients scheduled for TKA vs. THA. CONCLUSIONS: Considering the high prevalence of osteoporosis and osteopenia in elderly patients, DXA screening should be recommended for patients ≥ 70 years indicated for TKA.

Conductive Hearing Loss in the Hyp Mouse Model of X-Linked Hypophosphatemia Is Accompanied by Hypomineralization of the Auditory Ossicles.

X-linked hypophosphatemia (XLH) is a hereditary musculoskeletal disorder caused by loss-of-function mutations in the PHEX gene. In XLH, increased circulating fibroblast growth factor 23 (FGF23) levels cause renal phosphate wasting and low concentrations of 1,25-dihydroxyvitamin D, leading to an early clinical manifestation of rickets. Importantly, hearing loss is commonly observed in XLH patients. We present here data from two XLH patients with marked conductive hearing loss. To decipher the underlying pathophysiology of hearing loss in XLH, we utilized the Hyp mouse model of XLH and measured auditory brain stem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) to functionally assess hearing. As evidenced by the increased ABR/DPOAE threshold shifts in the mid-frequency range, these measurements indicated a predominantly conductive hearing loss in Hyp mice compared to wild-type (WT) mice. Therefore, we carried out an in-depth histomorphometric and scanning electron microscopic analysis of the auditory ossicles. Quantitative backscattered electron imaging (qBEI) indicated a severe hypomineralization of the ossicles in Hyp mice, evidenced by lower calcium content (CaMean) and higher void volume (ie, porosity) compared to WT mice. Histologically, voids correlated with unmineralized bone (ie, osteoid), and the osteoid volume per bone volume (OV/BV) was markedly higher in Hyp mice than WT mice. The density of osteocyte lacunae was lower in Hyp mice than in WT mice, whereas osteocyte lacunae were enlarged. Taken together, our findings highlight the importance of ossicular mineralization for hearing conduction and point toward the potential benefit of improving mineralization to prevent hearing loss in XLH. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Safety and performance of biodegradable magnesium-based implants in children and adolescents.

AIMS: Biodegradable magnesium-based alloy implants represent a promising option in orthopedic surgery, as the clinical outcomes have been reported to be comparable to those of titanium implants and no surgical interventions are required for removal. To date, little is known about the results of the use of these implants in children and adolescents. Therefore, the aim of the present study was to analyze the safety and performance of these implants in children and adolescents. PATIENTS AND METHODS: Eighty-nine patients treated with magnesium-based implants for fracture stabilization, osteotomy and osteochondral refixation were analyzed; 38 were treated by osteosynthesis; 18, osteotomy; and 33, osteochondral refixation. The mean follow-up duration was 8.2 months (range, 1.5-30 months). Clinical and radiographical follow-up examinations were performed at 4-8 weeks and 3-6 months, respectively, to evaluate implant performance and osseous consolidation. RESULTS: Clinical outcomes were rated as good to very good in all patients. Radiolucent zones were apparent after surgery in all patients but were noted to decrease in size during the follow-up period. Revision surgery was necessary in 1 of 89 patients who had a highly unstable osteochondritis dissecans lesion of the knee. None of the magnesium-based implants required surgical removal. CONCLUSION: Magnesium-based implants in children and adolescents results in good clinical outcomes when used for fracture stabilization, osteotomy and osteochondral defect refixation. Future studies are needed to further analyze the significance of the transient appearance and temporal development of radiolucent zones in the growing skeleton as well as the long-term performance of these implants.

[Musculoskeletal laboratory diagnostics in competitive sport]. / Muskuloskelettale Labordiagnostik im Leistungssport.

BACKGROUND: Laboratory diagnostics represent a valuable tool for the optimization and assessment of the performance and regeneration ability in professional athletes. Blood parameters play an important role in the prevention, diagnosis and rehabilitation of injuries and physical overload. OBJECTIVES: The aim of this article is to present an overview of musculoskeletal laboratory parameters and to provide relevant information for the medical care of competitive athletes. METHODS: Literature search and narrative review. RESULTS: The laboratory assessment of bone metabolism includes vitamin D, calcium and bone turnover and aims to provide a preventive benefit with respect to skeletal complications (e.g., to minimize the risk of bone stress injuries). In addition, muscular serum markers, such as lactate dehydrogenase (LDH), creatine kinase (CK), myoglobin and aspartate aminotransferase (AST) can be used to monitor metabolic adaptation to physical exercise and to obtain information about the muscular workload and potential damage. The energy availability can be estimated and optimized by appropriate balancing and laboratory determination of macro- and micronutrients. CONCLUSIONS: Laboratory diagnostics have a clinical relevance across different sport disciplines. They are intended to support athletes and medical staff on their way to the highest possible performance and help to ensure the optimal prevention of bone and muscle injuries. Parameters with deficiency results (e.g., vitamin D) should be adequately compensated. A periodization of the laboratory tests, with at least two tests per year, and the establishment of individual variability and reference ranges can improve the assessment.

Compound Heterozygous Frameshift Mutations in MESD Cause a Lethal Syndrome Suggestive of Osteogenesis Imperfecta Type XX.

Multiple genes are known to be associated with osteogenesis imperfecta (OI), a phenotypically and genetically heterogenous bone disorder, marked predominantly by low bone mineral density and increased risk of fractures. Recently, mutations affecting MESD, which encodes for a chaperone required for trafficking of the low-density lipoprotein receptors LRP5 and LRP6 in the endoplasmic reticulum, were described to cause autosomal-recessive OI XX in homozygous children. In the present study, whole-exome sequencing of three stillbirths in one family was performed to evaluate the presence of a hereditary disorder. To further characterize the skeletal phenotype, fetal autopsy, bone histology, and quantitative backscattered electron imaging (qBEI) were performed, and the results were compared with those from an age-matched control with regular skeletal phenotype. In each of the affected individuals, compound heterozygous mutations in MESD exon 2 and exon 3 were detected. Based on the skeletal phenotype, which was characterized by multiple intrauterine fractures and severe skeletal deformity, OI XX was diagnosed in these individuals. Histological evaluation of MESD specimens revealed an impaired osseous development with an altered osteocyte morphology and reduced canalicular connectivity. Moreover, analysis of bone mineral density distribution by qBEI indicated an impaired and more heterogeneous matrix mineralization in individuals with MESD mutations than in controls. In contrast to the previously reported phenotypes of individuals with OI XX, the more severe phenotype in the present study is likely explained by a mutation in exon 2, located within the chaperone domain of MESD, that leads to a complete loss of function, which indicates the relevance of MESD in early skeletal development. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

Bilateral Looser zones or pseudofractures in the anteromedial tibia as a component of medial tibial stress syndrome in athletes.

PURPOSE: Medial tibial stress syndrome (MTSS) represents a common diagnosis in individuals exposed to repetitive high-stress loads affecting the lower limb, e.g., high-performance athletes. However, the diagnostic approach and therapeutic regimens are not well established. METHODS: Nine patients, diagnosed as MTSS, were analyzed by a comprehensive skeletal analysis including laboratory bone turnover parameters, dual-energy X-Ray absorptiometry (DXA), and high-resolution peripheral quantitative computed tomography (HR-pQCT). RESULTS: In 4/9 patients, bilateral pseudofractures were detected in the mid-shaft tibia. These patients had significantly lower levels of 25-hydroxycholecalciferol compared to patients with MTSS but similar levels of bone turnover parameters. Interestingly, the skeletal assessment revealed significantly higher bone mineral density (BMD) Z-scores at the hip (1.3 ± 0.6 vs. - 0.7 ± 0.5, p = 0.013) in patients with pseudofractures and a trend towards higher bone microarchitecture parameters measured by HR-pQCT at the distal tibia. Vitamin D supplementation restored the calcium-homeostasis in all patients. Combined with weight-bearing as tolerated, pseudofractures healed in all patients and return to competition was achieved. CONCLUSION: In conclusion, deficient vitamin D levels may lead to pseudofractures due to localized deterioration of mineralization, representing a pivotal component of MTSS in athletes with increased repetitive mechanical loading of the lower limbs. Moreover, the manifestation of pseudofractures is not a consequence of an altered BMD nor microarchitecture but appears in patients with exercise-induced BMD increase in combination with reduced 25-OH-D levels. The screening of MTSS patients for pseudofractures is crucial for the initiation of an appropriate treatment such as vitamin D supplementation to prevent a prolonged course of healing or recurrence. LEVEL OF EVIDENCE: III.

Bone healing and reactivation of remodeling under asfotase alfa therapy in adult patients with pediatric-onset hypophosphatasia.

Hypophosphatasia (HPP) is a hereditary musculoskeletal disorder caused by inactivating variants in the ALPL gene and subsequently reduced serum tissue-nonspecific alkaline phosphatase (TNSALP) activity. This inborn error of metabolism results in decreased bone quality, accumulations of osteoid, and reduced bone mineralization. Increased incidence of fractures and prolonged bone healing are characteristic features for HPP. Available enzyme replacement therapy (asfotase alfa), was reported to recover bone mineralization and bone quality in adult HPP patients. Moreover, it was shown that asfotase alfa improved fracture healing of former nonunions in two adult HPP patients. We hypothesized that the nonunions are filled partially with osteoid, offering great potential to benefit from the treatment with asfotase alfa to promote bone healing. In the present study, we report three adult patients with pediatric-onset HPP and detected ALPL-mutations with prolonged bone healing after arthrodesis, tibial stress fracture, and osteotomy. After the initiation of asfotase alfa, immediately increased levels of alkaline phosphatase (ALP) and bone-specific ALP, as well as decreased levels of pyridoxal-5-phosphate (PLP), were detected in biochemical analysis. Importantly, even after up to 5 years of non-healing, a progredient consolidation was shown, assessed by a custom three-dimensional evaluation of repeated cone-beam computed tomography (CBCT) images, characterized by rapidly increasing levels of bone volume per tissue volume (BV/TV) within the volume of interest (i.e., the region of the non-healing bone). These radiographical findings were in line with the reported restoration of functional ability and pain-free full weight-bearing, as well as increased neuromuscular parameters (e.g., improved muscle strength). Taken together, our findings indicate that asfotase alfa improves the osseous consolidation of nonunions likely due to re-mineralization of osteoid tissue filling the former gap and improving the functional ability in adult HPP patients, characterized by increasing levels of BV/TV assessed via an innovative three-dimensional evaluation of CBCT images.

Ultra-high matrix mineralization of sperm whale auditory ossicles facilitates high sound pressure and high-frequency underwater hearing.

The auditory ossicles-malleus, incus and stapes-are the smallest bones in mammalian bodies and enable stable sound transmission to the inner ear. Sperm whales are one of the deepest diving aquatic mammals that produce and perceive sounds with extreme loudness greater than 180 dB and frequencies higher than 30 kHz. Therefore, it is of major interest to decipher the microstructural basis for these unparalleled hearing abilities. Using a suite of high-resolution imaging techniques, we reveal that auditory ossicles of sperm whales are highly functional, featuring an ultra-high matrix mineralization that is higher than their teeth. On a micro-morphological and cellular level, this was associated with osteonal structures and osteocyte lacunar occlusions through calcified nanospherites (i.e. micropetrosis), while the bones were characterized by a higher hardness compared to a vertebral bone of the same animals as well as to human auditory ossicles. We propose that the ultra-high mineralization facilitates the unique hearing ability of sperm whales. High matrix mineralization represents an evolutionary conserved or convergent adaptation to middle ear sound transmission.