Objective. While the short-stem design is not a new concept, interest has risen with increasing utilization of less invasive techniques. Especially, short stems are easier to insert through the direct anterior approach. In the radiographic evaluation of patients who underwent primary uncemented total hip arthroplasty (THA) using a TaperLoc Microplasty femoral component (Biomet, Warsaw, IN, USA), cortical hypertrophy was occasionally detected on three-month postoperative radiographs. The purpose of this study was to evaluate the radiographic changes associated with cortical hypertrophy of the femur three months postoperatively. Methods. Between May 2010 and September 2014, 645 hips in 519 patients who received the TaperLoc Microplasty stem were evaluated. Six hips in four patients were lost to follow-up. Finally, 639 hips in 515 patients were included in this study; 248 hips underwent bilateral simultaneous THA and 391 hips underwent unilateral THA. There were 103 males and 412 females (average age, 63 ± 10.1 years; average height, 156 ± 8.13 cm; and average weight, 58 ± 12.2 kg). The postoperative radiographs immediately taken after the operation and three months postoperatively were compared. We evaluated cortical hypertrophy around the stem. Cortical hypertrophy >2 mm on anterior-posterior X-ray was defined as “excessive periosteal reaction” (Figure 1). Results. Twenty-four (3.76%) of the 639 hips had an excessive periosteal reaction. Eight (1.25%) hips underwent bilateral simultaneous THA and sixteen (2.5%) hips underwent unilateral THA. With regard to the prevalence of the excessive periosteal reaction, there were no significant differences between the patients who underwent the unilateral procedure compared with those who underwent the bilateral procedure. Of these 24hips, 12 (50%) showed thigh pain in patients after surgery. The patients with an excessive periosteal reaction had an average age of 66 ± 9.02 years, an average height of 157 ± 6.4 cm, and an average weight of 61 ± 10.3 kg. There were no significant differences in age, height, and weight between the patients with an excessive periosteal reaction and all study patients. The thigh pain resolved spontaneously within three months after surgery in all patients, and no patient required revision surgery. Six (0.94%) hips had femoral periprosthetic fractures in the early postoperative period. Conclusions. Excessive periosteal reaction, which was defined as cortical hypertrophy >2 mm on anterior-posterior X-ray three month postoperatively, occurred in 3.75% of the patients who received the TaperLoc Microplasty stem. Thigh pain occurred in half of the patients who had an excessive periosteal reaction. We speculated that this reaction was caused by the concentration of the torque or vertical load on the limited area of the femur in the early postoperative period. This stress was accompanied by femoral periprosthetic fractures in the early postoperative period, and patients without femoral periprosthetic fractures experienced an excessive periosteal reaction with thigh pain

Aim. The aim of this study was to determine whether the absence of periosteal reaction on plain radiographs was predictive of exchange nail failure in lower limb diaphyseal fracture non-unions. Methods. A consecutive cohort of 20 femora and 35 tibiae undergoing exchange nailing for diaphyseal aseptic (n=39) and septic (n=16) fracture non-union at a single centre from 2003 to 2010. Multiple causes of non-union were found in 29 patients (53%) with infection present in 16 cases (29.1%). Of this cohort 49 fracture non-unions had complete radiographic records (19 femora and 30 tibiae) allowing evaluation of the periosteal callus. The primary outcome was the number of number of revision procedures required to achieve union. Failure was defined was as the requirement of >two revision procedures to achieve union. Results. The absence of periosteal callus from the fracture site on all four cortices conferred a relative risk ratio (RRR) 5.00 (p=0.006) of exchange nail failure in septic fracture non-unions. Receiver operator characteristic curve analysis of number of cortices with periosteal reaction for predicting exchange nail (>two exchange nail procedures) failure in both septic and aseptic cases found an area under the curve of 0.79 (95% confidence interval 0.675–0.904, p<0.0001). The complete absence of callus within 5 mm of the fracture site had a 75% chance of requiring 3 or more exchange nails to obtain union. Conversely the presence periosteal callus on at least one cortex within 5mm of the fracture site had a 100% chance the fracture would unite following 1 or 2 exchange nail procedures. Conclusion. Careful radiographic analysis of lower limb diaphyseal non-union should be undertaken before exchange nailing. The absence of periosteal reaction on plain radiographs in septic fracture non-union is predictive of exchange nail failure

We present three cases of intramuscular haemangioma adjacent to bone in the lower limb. All patients had local pain during the third decade. Plain radiographs showed an irregular or hypertrophic periosteal reaction on the shaft of the fibula and an intramuscular mass adjacent to the bone with inhomogenous high signal intensity on MRI. These lesions mimic periosteal or parosteal tumours

Aims. Distraction osteogenesis with intramedullary lengthening devices has undergone rapid development in the past decade with implant enhancement. In this first single-centre matched-pair analysis we focus on the comparison of treatment with the PRECICE and STRYDE intramedullary lengthening devices and aim to clarify any clinical and radiological differences. Methods. A single-centre 2:1 matched-pair retrospective analysis of 42 patients treated with the STRYDE and 82 patients treated with the PRECICE nail between May 2013 and November 2020 was conducted. Clinical and lengthening parameters were compared while focusing radiological assessment on osseous alterations related to the nail’s telescopic junction and locking bolts at four different stages. Results. Osteolysis next to the telescopic junction was observed in 31/48 segments (65%) lengthened with the STRYDE nail before implant removal compared to 1/91 segment (1%) in the PRECICE cohort. In the STRYDE cohort, osteolysis initially increased, but decreased or resolved in almost all lengthened segments (86%) after implant removal. Implant failure was observed in 9/48 STRYDE (19%) and in 8/92 PRECICE nails (9%). Breakage of the distal locking bolts was found in 5/48 STRYDE nails (10%) compared to none in the PRECICE cohort. Treatment-associated pain was generally recorded as mild and found in 30/48 patients (63%) and 39/92 (42%) in the STRYDE and PRECICE cohorts, respectively. Temporary range of motion (ROM) limitations under distraction were registered in 17/48 (35%) segments treated with the STRYDE and 35/92 segments (38%) treated with the PRECICE nail. Conclusion. Osteolysis and periosteal reaction, implant breakage, and pain during lengthening and consolidation is more likely in patients treated with the STRYDE nail compared to the PRECICE nail. Temporary ROM limitations during lengthening occurred independent of the applied device. Implant-related osseous alterations seem to remodel after implant removal. Cite this article: Bone Joint J 2023;105-B(1):88–96

Aim. Radiologic signs such as radiolucent lines around the implant, hardware fracture or displacement and periosteal reaction have been considered suggestive of implant-associated infection. The goal of this study is to assess the correlation of these signs with confirmed internal fixation-associated infection evaluated in a prospective cohort. Method. We evaluated the radiologic appearance of preoperative standard x-ray images in 421 surgeries performed in 380 patients with internal fixation device in place (56.8% male, mean age 53 ± 17 years). This prospective study was performed in a large single center for musculoskeletal surgery from 2013–2017. Infection was suspected preoperatively in only 23.8% of the surgeries. The most common indications for surgeries in which infection was not suspected were nonunion (84 cases) and symptomatic hardware (57 cases). All removed implants were sent to sonication for biofilm removal and detection. In addition, several peri-implant tissue samples were collected. Radiographs were analyzed in a blinded fashion for signs of radiolucent lines around the implant before removal, hardware fracture or displacement, and soft periosteal reactions suggestive of infection. Diagnosis was established according to the IDSA criteria for PJI. Contingency tables were constructed to determine sensitivity and specificity, and to perform Chi-square tests to compare the presence of infection with radiological signs of infection. Results. Radiologic signs suggestive for infection were uncommon, including radiolucent lines in 48 cases (11.4%); hardware breakage in 542cases (12.4%); hardware displacement in 45 cases (10.7%); periosteal reaction in 30 cases (7.1%). Infection was confirmed in 27.6% of the surgeries, and radiological signs of infection were only marginally more common in this group. Only the presence of radiolucent lines (p = 0.47; OR = 1.86 [95% CI 1.00 – 3.38]) and periosteal reaction (p = 0.15; OR = 2.48 [1.17 – 5.26]) were significantly associated with confirmed infection. Sensitivity of radiolucent lines and periosteal reaction were low (16,4% and 12,1%, respectively), while specificity remained acceptable (90.5%and 94.8%, respectively). Conclusions. Radiologic signs of infection are uncommon, even in the context of a confirmed infection. Radiolucency surrounding the implant and the presence of a soft periosteal reaction were significantly associated with the presence of infection, though sensitivity of the signs remained very low

Aims. Due to its indolent clinical behaviour, the treatment paradigm of atypical cartilaginous tumours (ACTs) in the long bones is slowly shifting from intralesional resection (curettage) and local adjuvants, towards active surveillance through wait-and-scan follow-up. In this retrospective cohort study performed in a tertiary referral centre, we studied the natural behaviour of ACT lesions by active surveillance with MRI. Clinical symptoms were not considered in the surveillance programme. Methods. The aim of this study was to see whether active surveillance is safe regarding malignant degeneration and local progression. In total, 117 patients were evaluated with MRI assessing growth, cortical destruction, endosteal scalloping, periosteal reaction, relation to the cortex, and perilesional bone marrow oedema. Patients received up to six follow-up scans. Results. At the time of the first follow-up MRI, 8% of the lesions showed growth (n = 9), 86% remained stable (101), and 6% decreased in size (n = 7). During the third follow-up, with a mean follow-up time of 60 months (SD 23), 24 patients were scanned, of whom 13% had lesions that had grown and 13% lesions that had decreased in size. After 96 months (SD 37), at the sixth follow-up MRI, 100% of the lesions remained stable. None of the lesions showed malignant progression and although some lesions grew in size (mean 1 mm (SD 0.8)), no malignant progression occurred. Conclusion. We conclude that active surveillance with MRI is safe for ACTs in the long bones in the short- and mid-term follow-up. Cite this article: Bone Joint J 2024;106-B(1):86–92

Introduction. Stryde® lengthening nail has been recently withdrawn because of concerns about osteolysis and other bone lesions that have been observed early after implantation. The present study analyses the incidence and features of these bone lesions in our patients. Materials and Methods. This is a retrospective review of a series of patients from two centres specializing in limb reconstruction. Inclusion criteria was a history of surgery with Stryde® lengthening nail with more than one year follow-up available. All postoperative x-rays were and clinical notes were reviewed. Results. 36 patients with 75 bone segments were included. 11 (30.5%) patients and 32 (42.6%) bone segments were without any lesion. In 3 (8.3%) patients and 3 (4%) segments, osteolytic lesions only were noticed. 11(30.5%) patients and 14 (18.6%) segments had combined lytic lesions and periosteal reaction or cortical thickening. 12 (33.3%) patients and 26 (34.6%) segments developed only periosteal reaction or cortical thickening. 54.8% of patients with bilateral nailing had bilateral lesions. 52% of the patients with bone lesions reported late onset of pain after the completion of the lengthening. The average earliest interval that any of the lesions was noticed was 10.2 months post-surgery. Conclusions. Patients with Stryde® nails should be monitored clinically and radiologically at regular intervals until removal. The early failure and withdrawal of Precise Stryde® nail, is a significant event in the field of limb reconstruction; this study adds useful data to the growing pool of published data related to the this event

Aims. Limb-lengthening nails have largely replaced external fixation in limb-lengthening and reconstructive surgery. However, the adverse events and high prevalence of radiological changes recently noted with the STRYDE lengthening nail have raised concerns about the use of internal lengthening nails. The aim of this study was to compare the prevalence of radiological bone abnormalities between STRYDE, PRECICE, and FITBONE nails prior to nail removal. Methods. This was a retrospective case series from three centres. Patients were included if they had either of the three limb-lengthening nails (STYDE, PRECICE, or FITBONE) removed. Standard orthogonal radiographs immediately prior to nail removal were examined for bone abnormalities at the junction of the telescoping nail parts. Results. In total, 306 patients (168 male, 138 female) had 366 limb-lengthening nails removed. The mean time from nail insertion to radiological evaluation was 434 days (36 to 3,015). Overall, 77% of STRYDE nails (20/26) had bone abnormalities at the interface compared with only 2% of FITBONE (4/242) and 1% of PRECICE nails (1/98; p < 0.001). Focal osteolysis in conjunction with periosteal reaction at the telescoping interface was only observed in STRYDE nails. Conclusion. Bone abnormalities at the interface of telescoping nail parts were seen in the majority of STRYDE nails, but only very rarely with FITBONE or PRECICE nails. We conclude that the low prevalence of radiological changes at the junctional interface of 242 FITBONE and 98 PRECICE nails at the time of nail removal does not warrant clinical concerns. Cite this article: Bone Joint J 2021;103-B(11):1731–1735

Aims. The STRYDE nail is an evolution of the PRECICE Intramedullary Limb Lengthening System, with unique features regarding its composition. It is designed for load bearing throughout treatment in order to improve patient experience and outcomes and allow for simultaneous bilateral lower limb lengthening. The literature published to date is limited regarding outcomes and potential problems. We report on our early experience and raise awareness for the potential of adverse effects from this device. Methods. This is a retrospective review of prospective data collected on all patients treated in our institution using this implant. We report the demographics, nail accuracy, reliability, consolidation index, and cases where concerning clinical and radiological findings were encountered. There were 14 STRYDE nails implanted in nine patients (three male and six female) between June 2019 and September 2020. Mean age at surgery was 33 years (14 to 65). Five patients underwent bilateral lengthening (two femoral and three tibial) and four patients unilateral femoral lengthening for multiple aetiologies. Results. At the time of reporting, eight patients (13 implants) had completed lengthening. Osteolysis and periosteal reaction at the junction of the telescopic nail was evident in nine implants. Five patients experienced localized pain and swelling. Macroscopic appearances following retrieval were consistent with corrosion at the telescopic junction. Tissue histology was consistent with effects of focal metallic wear debris. Conclusion. From our early experience with this implant we have found the process of lengthening to be accurate and reliable with good regenerate formation and consolidation. Proposed advantages of early load bearing and the ability for bilateral lengthening are promising. We have, however, encountered concerning clinical and radiological findings in several patients. We have elected to discontinue its use to allow further investigation into the retrieved implants and patient outcomes from users internationally. Cite this article: Bone Joint J 2021;103-B(6):1168–1172

Introduction: Pediatric ankle trauma is common, and mostly a self limiting condition, with most children recovering within a few days to one week. However, some children seem to be affected more than others and to recover more slowly, despite normal radiographs. We set out to determine the occurrence of radiographically occult fractures, using high-resolution ultrasound. Material and Methods: Twenty consecutive, skeletally immature patients, aged from 5 to 13 years with acute ankle injury, and normal radiographs were referred for high resolution ultrasound during the first week after the injury. A follow-up radiograph, obtained 2–3 weeks after the injury, was assessed for periosteal reaction / callus formation. Results: In 13 patients there was no ultrasonographic evidence of fracture, nor was a periosteal reaction / callus formation. Six patients had ultrasonographic evidence of small fractures of the lateral malleolus, and periosteal reaction / callus formation on the follow-up film. In one patient a subcortical compression was evident on ultrasound. In this patient, although no periosteal reaction was observed on the follow up X-ray, a small fracture line became evident. Discussion: Small lateral malleolar fractures may be missed on standard ankle radiographs. In patients with a clinical presentation consistent with a fracture, high resolution ultra-sound is a highly sensitive and specific diagnostic tool

We investigated the effects of non-steroidal anti-inflammatory drugs (NSAIDs) with different cyclooxygenase (COX) selectivity on orthopaedic device-related infections (ODRIs) in a rat model. We aimed to measure the impact of NSAID therapy on bone changes, bacterial load, and cytokine levels after treatment with antibiotics. We also compared the effects of long vs short-term celecoxib (a COX-2 inhibitor) treatment on the same outcomes. Skeletally mature female Wistar rats were implanted with Staphylococcus epidermidis- contaminated polyetheretherketone (PEEK) screws in the proximal right tibia and monitored for 7 days. All animals received subcutaneous antibiotics (rifampicin plus cefazolin) for two weeks from day 7 to 21. In phase I of the study, rats were randomly assigned to receive 28 days of oral treatment with acetylsalicylic acid, ibuprofen, celecoxib, or vehicle control. In phase II, an additional group received seven days of celecoxib treatment from day 0 to 7. Bone changes were monitored using in vivo micro-CT and histology. Quantitative bacteriology was performed at euthanasia. Plasma samples were collected to measure cytokine levels on days 0, 6, 20, and 28. Combination antibiotic therapy resulted in treatment success in 85.71% of cases, while the addition of long-term celecoxib treatment reduced it to 45.45%. Long-term celecoxib treatment significantly reduced bone loss (33.85% mean difference [95% CI 14.12–53.58], p=0.0004 on day 6 bone fraction) and periosteal reaction (0.2760 μm mean difference [95% CI 0.2073–0.3448], p<0.0001 on day 14 periosteal thickness) during early infection compared to the control group. Short- term celecoxib treatment showed similar radiological results without a reduction in treatment success (88.9%). No differences in the inflammatory markers were observed. Our findings highlight the potential benefits of short-term use of celecoxib in improving bone fraction during the early post-infection period without impairing the efficacy of antibiotic therapy

We retrospectively reviewed 45 children treated between 1987 and 2002. Their mean age was 9 years (3 to 13). Fifteen patients had subacute osteitis. Only patients with Bledhill and Roberts type II, III and IV were included. Biopsy provided histological proof of subacute osteitis in nine patients, and six were successfully treated non-surgically with flucloxacillin. Six patients had Ewing’s sarcoma, 24 had osteosarcoma, 23 Enneking stage-IIB (extracompartmental) and one Enneking stage-IIA (intracompartmental). The preoperative clinical signs, radiographs and MRI studies were reviewed. On plain radiographs, cortical destruction and periosteal reaction were assessed. On MRI the extent and nature of bone marrow involvement and the size of the soft tissue mass/oedema was analysed and correlated clinically. On plain radiographs, cortical destruction was present in all patients with Ewing’s sarcoma and stage-IIB osteosarcoma and in 50% of patients with subacute osteitis. An ill-defined zone of transition was found in all patients with Ewing’s sarcoma and osteosarcoma and in 50% of those with subacute osteitis. These findings therefore did not help to differentiate between the two groups. The periosteal reaction was well-defined in subacute osteitis and lucencies between laminations were thin. In the malignant group the periosteal reaction was always ill-defined, with or without a Codman’s triangle, sunray spicules and hair-on-end. Lucencies between laminations were broad and broken. This was useful in differentiating between the two groups. On MRI, patients with subacute osteitis had no soft tissue mass, with an infiltrative type of bone marrow involvement. In the malignant group, the soft tissue mass was large and the bone marrow involvement well demarcated. We concluded that where there was a well-defined periosteal reaction on plain radiographs, and no soft tissue mass with infiltrative bone marrow involvement on MRI, patients could initially be treated as subacute osteitis without biopsy

Aim. In this study we investigated the effects of non-steroidal anti-inflammatory drugs (NSAIDs) with different cyclooxygenase (COX) selectivity on orthopaedic device-related infections (ODRIs) in a rat model. Specifically, we aimed to measure the impact of NSAID therapy on bone changes, bacterial load, and cytokine levels after treatment with antibiotics. In addition, we compared the effects of long vs short-term celecoxib (a COX-2 inhibitor) treatment on the same outcomes. Method. Skeletally mature female Wistar rats were implanted with Staphylococcus epidermidis-contaminated polyetheretherketone (PEEK) screws (1.5 × 10. 6. CFU per screw) in the proximal right tibia and monitored for 7 days. All animals received subcutaneous antibiotics (rifampicin plus cefazolin) for two weeks from day 7 to 21. In phase I of the study, rats were randomly assigned to receive 28 days of oral treatment with acetylsalicylic acid, ibuprofen, celecoxib, or vehicle control. In phase II, an additional group received seven days of celecoxib treatment from day 0 to 7. After implantation, bone changes were monitored using in vivo micro-CT and histology. Quantitative bacteriology was performed at euthanasia. Plasma samples were collected to measure cytokine levels at four time points (day 0, 6, 20, and 28). Results. The combination of antibiotic therapy resulted in treatment success in 85.71% of cases, while the addition of long-term celecoxib treatment reduced it to 45.45%. Long-term celecoxib treatment significantly reduced bone loss (33.85% mean difference [95% CI 14.12–53.58], p=0.0004 on day 6 bone fraction) and periosteal reaction (0.2760 μm mean difference [95% CI 0.2073–0.3448], p<0.0001 on day 14 periosteal thickness) during the early post-infection period compared to the control group. Short-term celecoxib treatment showed similar radiological results, however, there was no significant reduction in treatment success in the celecoxib group (88.9%). No differences in the selected inflammatory markers were observed. Conclusion. Our findings highlight the potential benefits of short-term use of celecoxib in improving bone fraction during the early post-infection period without impairing the efficacy of antibiotic therapy. This study suggests that celecoxib may be a useful addition to the multimodal approach to pain management in orthopaedic device-related infections

Florid reactive periostitis is a pronounced periosteal reaction, usually affecting the hands and feet, for which there is no obvious cause. It is rare in children and in long bones. We report an unusual case of florid reactive periostitis in a ten-year-old girl that involved both bones of the forearm. The lesion resolved over a period of one year, leaving a residual exostosis. She developed a physeal bar in the distal ulna in the region of the lesion at one-year follow-up. This was thought to be a complication of the biopsy procedure and was treated by resection and proximal ulnar lengthening

Introduction. The STRYDE nail is an evolution of the PRECICE Intramedullary Limb Lengthening System, with unique features regarding its composition. It is designed for load bearing throughout treatment in order to improve patient experience and outcomes and allow for simultaneous bilateral lower limb lengthening. The literature published to date is limited with regards to both outcomes and potential issues. In this paper we report on our early experience and raise awareness for the potential of adverse effects from this device. Materials and Methods. This is a review of all patients treated in our institution using this implant. Data were prospectively recorded. We report on demographics, nail accuracy, reliability, consolidation index and cases where concerning clinical and radiological findings were encountered. Results. 14 Stryde nails were implanted in nine patients (three males and six females) between June 2019 and September 2020. Mean age at surgery was 33 years old (14–65 years old). Five patients underwent bilateral lengthening (two femoral and three tibial) and four patients unilateral femoral lengthening for multiple aetiologies. By the time of this report eight patients (13 implants) had completed lengthening. Osteolysis and periosteal reaction at the junction of the telescopic nail was evident in nine implants. Five patients experienced localised pain and swelling. Macroscopic appearances following retrieval were consistent with corrosion at the telescopic junction. Tissue histology was consistent with effects of focal metallic wear debris. Conclusions. From our early experience with this implant we have found the process of lengthening to be accurate and reliable with good regenerate formation and consolidation. Proposed advantages of early load bearing and the ability for bilateral lengthening are promising. We have, however, encountered cases with concerning clinical and radiological findings. We have elected to discontinue its use to allow further investigation into the retrieved implants and patient outcomes from users internationally

Introduction. IM (Intra Medullary) nail fixation is the standard treatment for diaphyseal femur fractures and also for certain types of proximal and distal femur fractures. Despite the advances in the tribology for the same, cases of failed IM nail fixation continue to be encountered routinely in clinical practice. Common causes are poor alignment or reduction, insufficient fixation and eventual implant fatigue and failure. This study was devised to study such patients presenting to our practice and develop a predictive model for eventual failure. Materials and Methods. 57 patients who presented with failure of IM nail fixation (± infection) between Jan 2011 – Jun 2020 were included in the study and hospital records and imaging reviewed. Those fixed with any other kinds of metalwork were excluded. Classification for failure of IM nails – Type 1: Failure with loss of contact of lag screw threads in the head due to backing out and then rotational instability, Type 2A: Failure of the nail at the nail and lag screw junction, Type 2B: Failure of the screws at the nail lag screw junction, Type 3: Loosening at the distal locking sites with or without infection. X-rays reviewed and causes/site of failure noted. Results. Total patients - 57. Demography - Average age - 58.9 years, 22 Males and 35 females. Eleven patients were noted to have an infection at the fracture site that needed oral or IV antibiotics.16 patients - at least 1 cerclage wire for fracture reduction and fixation + IM Nail. Subtrochanteric fractures (42/57) were the most common to fail. In those fractures with postero-medial comminution, locking of the lag screw in position thus preventing backout can prevent failure. In type 2 failures, preventing varus fixation by early open reduction and temporary fixation with plates and screws can achieve improved results. Those with type 3 failures with periosteal reaction should be considered to be infected until proven otherwise. Conclusions. This classification for failure of IM nails in the femur can be used as a predictive model for failures and allow early recognition and intervention to tackle them

Introduction and Objective. Heterotopic ossification is the formation of extraskeletal mineralized tissue commonly associated with either trauma or surgery. While several mouse models have been developed to better characterize the pathologic progression of HO, no model currently exists to study HO of the hip, the most common location of acquired HO in patients. Owing to the unique biological mechanisms underpinning the formation of HO in different tissues, we sought to develop a model to study the post-surgical HO of the hip. Materials and Methods. Wild-type mice C57BL/6J mice were used to study the procedure outcomes, while Pdgfra-CreERT2;mT/mG and Scx-GFP reporter animals were used for the lineage tracing experiments (total n=16 animals, male, 12 weeks old). An anterolateral approach to the hip was performed. Briefly, a 2 cm incision was made centered on the great trochanter and directed proximal to the iliac crest and distally over the lateral shaft of the femur. The joint was then reached following the intermuscular plane between the rectus femoris and gluteus medius muscles. After the joint was exposed, the articular cartilage was removed using a micropower drill with a 1.2 mm reamer. The medius gluteus and superficial fascia were then re-approximated with Vicryl 5-0 suture (Ethicon Inc, Somerville, NJ) and skin was then closed with Ethilon 5-0 suture (Ethicon Inc). Live high resolution XR imaging was performed every 2 wks to assess the skeletal tissues (Faxitron Bioptics, Tucson, AZ). The images were then scored using the Brooker classification. Ex-vivo microCT was conducted using a Skyscan 1275 scanner (Bruker-MicroCT, Kontich, Belgium). 3D reconstruction and analysis was performed using Dragonfly (ORS Inc., Montreal, Canada). For the histological analysis of specimens, Hematoxylin and Eosin (H&E), modified Goldner's Trichrome (GMT) stainings were performed. Reporter activity was assessed using fluorescent imaging. Results. Substantial periarticular heterotopic bone was seen in all cases. A periosteal reaction and an initial formation of calcified tissue within the soft tissue was apparent starting from 4 wks after surgery. By XR, progressive bone formation was observed within the periosteum and intermuscular planes during the subsequent 8 weeks. Stage 1 HO was observed in 12.5% of cases, stage 2 in 62.5% of cases, and stage 3 HO in 25% of cases. 3D microCT reconstructions of the treated hip joints demonstrated significant de novo heterotopic bone in several location which phenocopy human disease. Heterotopic bone was observed in an intracapsular location, periosteal location involving the iliac bone and proximal femur, and intermuscular locations. Histological analyses further confirmed these findings. To assess the cells which gave rise to HO in this model, an inducible PDGFRα and constitutive Scx-GFP reporter mice were used. A dramatic increase in mGFP reporter activity was noted PDGFRα within the HO injury site, including in areas of new cartilage and bone formation. Scx-associated reporter activity increased in the soft tissue and periosteal periacetabular areas of injured hips. Conclusions. HO has a diverse set of pathologies, of which joint associated HO after elective surgery is the most common. Here, we present the first mouse model of hip dislocation and acetabular reaming that mimics elements of human periarticular HO. The diverse locations of HO after acetabular reaming (intracapsular, intermuscular and periosteal) suggests the activation of different and specific HO program after surgery. Such a field effect would be consistent with local trauma and inflammation, which is a well-studied contributor to HO genesis. Not surprisingly, joint-associated HO significantly derives from PDGFRα-expressing cells, which has been shown to similarly give rise to intramuscular and intratendinous HO

The “Toddler Fracture” is an un-displaced oblique distal tibia fracture seen in children 9–36months of age presenting with refusal to walk, often after an unwitnessed or minor injury. Diagnosis is often made clinically, because initial x-rays are negative in up to 50% of patients, and then confirmed by the presence of periosteal reaction on follow up x-ray 7–10 days later. Point of Care Ultrasound (POCUS) has shown excellent ability to detect distal radius, clavicle and other extremity fractures and published case reports suggest that POCUS can also detect Toddler Fractures. The objective of this proof of concept study was to establish the feasibility and preliminary sensitivity and specificity of POCUS in the diagnosis of Toddler Fractures, and to characterize the POCUS findings in patients presenting with clinical Toddler Fractures. This was a prospective reviewer-blinded cross-sectional study of patients presenting to the emergency department of a paediatric tertiary care centre with presumed toddler fractures. All patients with suspected toddler fracture underwent lower limb x-ray. Those enrolled in the study also underwent POCUS of both lower extremities by a specialized provider. Treating clinicians were blinded to ultrasound results, and study sonographers were blinded to x-ray results. Study patients were then seen in paediatric orthopaedic follow up clinics 7–10 days later, and clinical assessment and follow up x-ray were performed as necessary to confirm diagnosis. Toddler Fracture was confirmed in 5 of 27 patients enrolled in the study. Preliminary results demonstrate that these POCUS findings were detected on the scan in all 5 confirmed toddler fractures. Three of these patients had an initial positive x-ray and 2 went on to have toddler fracture confirmed on follow up x-ray and orthopaedic assessment. POCUS findings consistent with a toddler fracture were found to be cortical disruption and periosteal hematoma. POCUS may be a useful adjunct to confirming a diagnosis of a toddler fracture when clinical suspicion is high and initial x-ray is negative. This pilot study provides positive impetus for further prospective study. The use of POCUS to confirm toddler fracture can decrease further radiation exposure to patients, allow early guidance to families on the management and expected recovery, and has potential to decrease burden on families and the healthcare system by potentially eliminating unnecessary follow-up appointments. Future study will help to better guide diagnostic and technical criteria, and provide guidance for appropriate medical education in this technique and interpretation

Purpose: The purpose of this study was to evaluate centromedullary pinning for bone lengthening. We studied an animal model to discover the details of bone regeneration and assess the advantages of the technique. We present our early clinical results. Material and methods: Progressive lengthenings of the tibia by centromedullary pinning were performed in eleven dogs. Distraction began on day 5 and lasted 28 days. Arteriograms were obtained after sacrifice.We also analysed 17 cases of limb lengthening in patients: one arm, two forearms, nine femurs, five tibias. Mean patient age was 14 years. Mean gain in bone length was 6.2 cm. Results: The experimental work demonstrated that intensive bone regeneration requires faster distraction. Early bone union was observed in four dogs. Bone healing was complete at about 15 days in all dogs. The centromedullary pins were left in place in three dogs after removing the external fixator. There was no secondary deformation. The arteriogram showed that the nourishing artery was not ruptured. In our patients, delay to healing was shorter. The radiograms demonstrated intensive bone regeneration. Endosteal regeneration was significant and was never inhibited. Significant periosteal reaction was observed. The planned gain in length was achieved in all patients. We did not have any complications. Discussion: Bone lengthening methods using a centromedullary nail provide absolute stability while avoiding external fixation but at the cost of complete destruction of the centromedullary vascular supply. Our animal experiments and clinical experience prove that elastic centromedullary pins do not inhibit endosteal regeneration but, on the contrary, partial destruction of the marrow with intact vascularisation stimulates bone regeneration. For bone lengthenings, centromedullary pinning is the only method of internal fixation allowing optimal conditions for bone regneration. Conclusion: The progressive distraction of the elastic centromedullary pin during the lengthening period stimulates the regenerative processes. The biological effect of the vascular “displacement” from the centre to the periphery of the bone fragments leads to significant periosteal reaction. Elastic centromedullary pinning adds stability to the bone fragments. Associating the two methods allows removal of the external fixator leaving the centromedullary pins in place. By strengthening the regenerated bone, the pins provide a certain degree of additional stability

Aims

Low-grade central osteosarcoma (LGCOS), a rare type of osteosarcoma, often has misleading radiological and pathological features that overlap with those of other bone tumours, thereby complicating diagnosis and treatment. We aimed to analyze the clinical, radiological, and pathological features of patients with LGCOS, with a focus on diagnosis, treatment, and outcomes.