The role of radiotherapy for prevention of heterotopic ossification after major hip surgery

Genetic regulation of injury-induced heterotopic ossification in adult zebrafish

Heterotopic ossification is the inappropriate formation of bone in soft tissues of the body. It can manifest spontaneously in rare genetic conditions or as a response to injury, known as acquired heterotopic ossification. There are several experimental models for studying acquired heterotopic ossification from different sources of damage. However, their tenuous mechanistic relevance to the human condition, invasive and laborious nature and/or lack of amenability to chemical and genetic screens, limit their utility. To address these limitations, we developed a simple zebrafish injury model that manifests heterotopic ossification with high penetrance in response to clinically emulating injuries, as observed in human myositis ossificans traumatica. Using this model, we defined the transcriptional response to trauma, identifying differentially regulated genes. Mutant analyses revealed that an increase in the activity of the potassium channel Kcnk5b potentiates injury response, whereas loss of function of the interleukin 11 receptor paralogue (Il11ra) resulted in a drastically reduced ossification response. Based on these findings, we postulate that enhanced ionic signalling, specifically through Kcnk5b, regulates the intensity of the skeletogenic injury response, which, in part, requires immune response regulated by Il11ra.

Treatment of heterotopic ossification of the hip with use of a plaster cast: case report

Heterotopic ossification can be defined as the formation of bone in tissues that have no ossification properties, such as in muscles and connective tissue of a periarticular region, without invasion of the joint capsule. This pathology usually has a benign course, but it can cause a reduction in the range of joint movement and hamper the rehabilitation process. Its etiology is still unknown and it usually is originated from posttraumatic complications, affecting 10–20% of patients with traumatic brain injury. Among its clinical manifestations, it may present pain and limitation of joint movement, heat, edema, and local flushing. In some cases, it can present moderate fever, severe spasticity, and even ankylosis in more advanced stages of the disease. Treatment is based on resection of the ossification, with adjuvant measures such as non-steroidal anti-inflammatory drugs, bisphosphonate, radiotherapy, and physical therapy. None of these methods currently have a precise recommendation regarding dose, quantity, or well-established protocols. Still, the best treatment is prevention. The objective of this report is to describe a case of heterotopic ossification in the hip after traumatic brain injury, presenting the clinical manifestations and discussing the treatment instituted with a long leg plaster cast.

Computerized tomography-based radiotherapy improves heterotopic ossification outcomes

PURPOSE

To report the impact of computerized tomography (CT) based radiotherapy (RT) on heterotopic ossification (HO) outcomes.

METHODS

This is a single institution, retrospective study of 532 patients who were treated for traumatic acetabular fractures (TAF). All patients underwent open-reduction internal-fixation (ORIF) of the TAF followed by RT for HO prophylaxis. Postoperative RT was delivered within 72h, in a single fraction of 7Gy. The patients were divided into 2 groups based on RT planning: CT (A) vs. clinical setup (B).

RESULTS

At a median follow up of 8years the incidence of HO was 21.6%. Multivariate regression analysis revealed that group (A) vs. (B) had HO incidence of 6.6% vs. 24.6% (p<0.001), respectively. Furthermore, HO Brooker grade ≥3 was observed in 2.2% vs. 10.8% (p=0.007) in group (A) vs. (B), respectively. Thus, the odds of developing HO and Brooker grades ≥3 were 4.7 and 4.5 times higher, respectively, in patients who underwent clinical setup.

CONCLUSION

Our data suggest that using CT based RT allowed more accurate delineation of the tissues and better clinical outcomes. Although CT-based RT is associated with additional cost the efficacy of CT-based RT reduces the risk of HO, thereby decreasing the need for additional surgical interventions.

Heterotopic ossification in vertebral interlaminar/interspinous instrumentation: report of a case

We present here a rare case of heterotopic ossification in interspinous/interlaminar Coflex device. The classical surgical indications for these implants are degenerative canal stenosis, discogenic low back pain, disk herniations, facet syndrome, and instability. However, fractures of spinous processes are a potential risk after interspinous/interlaminar devices' implantation. Recently, heterotopic ossification, a well-known complication of hip and knee arthroplasty, has been reported after cervical and lumbar prosthesis. We performed undercutting and implantation of the dynamic interspinous/interlaminar device to treat an adult male patient with L4-L5 stenosis. The patient underwent 45-day imaging and clinical followup, and we observed both a neurological and imaging improvement. A CT bone scan, performed 3 years after surgery for recurrence of neurogenic claudication, showed a new stenosis due to an abnormal ossification all over the device. To our knowledge, this is the first reported case of heterotopic ossification in an interspinous/interlaminar dynamic device. Accordingly, we aim to suggest it as a new complication of interspinous/interlaminar devices.

Prophylaxis of heterotopic ossification - an updated review

Heterotopic ossification (HO) is defined as the process by which trabecular bone forms outside of the skeletal structure, occupying space in soft tissue where it does not normally exist. The current popular prophylactic treatment modalities include non-steroidal anti-inflammatory drugs (NSAIDs) and radiation therapy, although the literature remains inconclusive as to which is superior. Additionally, both treatments can lead to adverse effects to the patient. Recently there have been several studies attempting to identify new aspects of the etiology of heterotopic bone formation and introduce new prophylactic modalities with increased efficacy and fewer side effects. For this review, we selectively retrieved articles from Medline published from 1958–2008 on the prophylaxis of HO with the aim of assisting readers in quickly grasping the current status of research and clinical aspects of HO prophylaxis.

Re-irradiation to prevent ectopic bone formation after major hip surgery

Ectopic bone formation may occur after total hip arthroplasty, but fortunately most patients are asymptomatic. Both pre-operative and post-operative radiotherapy are effective in prevention of ectopic bone formation. In the few patients who needed re-operation, we found that re-irradiation is possible and safe. This case report presents our experience with single dose reirradiation of the hip in an attempt to prevent post-operative ectopic bone formation.