Issue: December 2016
December 14, 2016
7 min read

Diagnosis, treatment advances help reduce incidence of heterotopic ossification

Heterotopic ossification has been shown to occur in the absence of a meticulous arthroplasty or arthroscopy surgical technique.

Issue: December 2016
You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

Heterotopic ossification, which is bone that forms in an undesired location following a musculoskeletal injury or surgical procedure, is a problem among orthopaedic patients. It can occur following trauma; fractures, such as those of the acetabulum; fracture dislocations of the radius or ulna; total joint reconstruction; hip resurfacing; hip arthroscopy; total disc arthroplasty; spinal cord injuries; and other clinical scenarios.

When heterotopic ossification (HO) is severe or problematic and causes pain, or affects a patient’s mobility and function, it should be managed by an orthopaedic surgeon. Occasionally, that involves surgery or a revision procedure to resolve the problem.

Pierre Hoffmeyer, MD, who studied the role of NSAIDs in the management of HO after total hip replacement (THR) with Saudan and colleagues at University Hospitals Geneva in Switzerland, told Orthopaedics Today Europe, “Heterotopic ossification is not the problem it used to be, and we do not know why.”

Pierre Hoffmeyer, MD
Pierre Hoffmeyer

However, it is a disease that has not fully disappeared either, he said.

Minimize heterotopic ossification

There appears to be an overall reduction in severe cases of HO in orthopaedic patients from what was reported in the 1980s and 1990s, Hoffmeyer said. Therefore, the newer surgical techniques being used may be associated with the overall reduced incidence of HO being reported, he added.

“It may be that faster surgery and better surgery does less damage to the muscle tissue. The use of pulsed lavage is probably also something that has had an effect on the HO problem. We mobilize patients faster. Maybe that helps, too,” Hoffmeyer said.

Techniques to implant the latest generation of total disc arthroplasty (TDA) prostheses, which are fixed in a way that is less invasive and damaging to the vertebral bodies than earlier designs, may perhaps be associated with a reduced incidence of HO, according to Christoph Mehren, MD, of Munich, Germany.

Christoph Mehren, MD
Christoph Mehren

“The implantation is quick now so it is comparable to putting in cage [for a] fusion. It is much easier than the first generation,” Mehren said, noting that excessive bony work during TDA can result in ossification, which can evolve into a fusion.

Patient, surgical factors

Based on the literature and comments Orthopaedics Today Europe received from Ali Bajwa, MPhil, FRCS(Orth), reports of problematic heterotopic bone in conjunction with hip surgery that addresses the hip capsule show it is amenable to arthroscopic treatment. This is mostly done in younger, athletic men.

“Heterotopic ossification, in our hands, requiring treatment is one in 1,500,” Bajwa, of London, told Orthopaedics Today Europe. However, he said its incidence may be higher.

According to Bajwa, patients develop HO after hip arthroscopy based on patient factors, such as having a bulky or extremely muscular physique. Gender is also a factor, with more men than women developing it following hip arthroscopy. There are also key surgical factors associated with HO development, he said, such as when the muscles and the hip capsule muscles are violated or the two ends of a partial capsulectomy are not fully brought together at the end of the procedure.

Careful surgery required

“The mesenchymal stems cells (MSCs) have not been associated with increased HO,” Bajwa said.

He noted when patients undergo hip arthroscopy for acetabular impingement, HO may occur at the hip capsule. One way to reduce the risk of HO in hip arthroscopy cases is to use meticulous surgical management, which includes, but is not limited to, removing all the bone debris that high-speed burrs create using simultaneous high-flow washout.

“With any surgery, be it hip arthroscopy or any other aspect of orthopaedic surgery, if you do not have good control of postoperative bleeding or hemostasis, you have got a slightly higher risk of HO,” Bajwa said.


HO in the spine

Spinal cord injury (SCI) is a spine condition associated with the development of HO.

“Historically, it has been an early finding in patients with SCI that they do develop HO, typically around the joints, and also some ossifications in some of the muscle. I think, generally speaking, the pathophysiology which is inducing this ossification is still not well known,” Armin Curt, MD, of the University of Zurich Spinal Cord Injury Center at Balgrist University Hospital in Zurich, told Orthopaedics Today Europe.

Ali Bajwa, MPhil, FRCS(Orth)
Ali Bajwa

He said discussions have focused on whether microtrauma or intensive physiotherapy and the stretching associated might play accelerate the development of HO.

“But this has never been proven,” Curt said.

A minor problem in TDA

Heterotopic ossification can occur after cervical and lumbar TDA in all types of patients who undergo this procedure, but it is slightly more common in patients who present with ossification of the anterior ligament. Gender plays no role in the development of HO after TDA, Mehren said.

He described HO in conjunction with TDA as “slow fusion.”

“Especially in the cervical spine, the HO is more an issue for the surgeons and for the industry and insurance [companies],” he said.

There is a greater incidence of HO in cervical than lumbar TDA, Mehren said. Overall, the clinical impact of HO on TDA is minimal.

Norbert Weidner, MD, of the Spinal Cord Injury Center at Heidelberg University Hospital in Heidelberg, Germany, told Orthopaedics Today Europe published SCI research suggests patients with a rather complete SCI who receive physical therapy (PT) that is too aggressive are more prone to HO. On the other hand, he noted, some publications claim immobilization of patients with severe SCI or severe brain damage also leads to the HO.

Armin Curt, MD
Armin Curt

“I would neither say that it is the immobilization or the intense PT that is a particular risk factor for having this condition,” Weidner said.

NSAIDs to reduce HO risk

Following THR, Hoffmeyer, who is an Orthopaedics Today Europe Editorial Board member, he has seen bridging bone between the pelvis and femur that he considers HO and NSAIDs can be used postoperatively to prevent that. In their randomized study Hoffmeyer, Saudan and colleagues found fewer adverse events using 200-mg celecoxib twice daily for 10 days postoperatively to prevent HO than using 400-mg ibuprofen three times daily. They concluded celecoxib also did a better job than ibuprofen of preventing radiographic HO.

Other clinicians use indomethacin, naproxen, aspirin and low-dose heparin to prevent HO in THR, SCI and other settings.

Various treatment approaches

HO treatments orthopaedic and spine surgeons typically use include NSAID medications. Indomethacin is typically administered to SCI patients at Curt’s center a few weeks after their injury.

Norbert Weidner, MD
Norbert Weidner

Weidner said if HO is going to develop in a spinal cord injured patient, it is within 4 weeks to 8 weeks postinjury and is more prevalent in patients who are grade A or B on the American Spinal Injury Association Impairment Scale classification. In these cases, using NSAIDs to treat HO early, when its initial signs are seen on MRI, is the first line of treatment, he said.

NSAIDS, “in particular also with the improved diagnostics we frequently use,” are making a difference in outcomes, Weidner said.

Spinal cord injury specialists should also look for other signs of HO, such as swelling, pain or redness around the patient’s joints. When these are seen in Weidner’s patients, in the absence of any real bone formation, patients are immediately transferred for an MRI, he said.

“I think that helps dramatically reduce the bone formation in a quantity that really disables the patient. I think the MRI is probably part of the solution to treat patients early,” Weidner said.


Surgical excision, radiotherapy

“In worse cases, where sometimes we go in arthroscopically to excise heterotopic bone, for instance, then there is a role for perioperative radiotherapy,” Bajwa said.

In recent years, Weidner’s group has only encountered a few cases in which a transfer for a surgical intervention by an orthopaedic surgeon at Heidelberg University Hospital was required. He explained surgery is reserved for SCI patients who cannot transfer from a wheelchair because they cannot bend enough at the hips, for example.

“The additional disability due to this ossification is not so strong to justify such a surgery. The risk is there that if you go in and remove the bone, then you cause, of course, additional trauma to the muscles and the joint and the surrounding tissue that may create a new stimulus for new bone formation,” Weidner said. Surgery is usually done in conjunction with one 5 Gy radiotherapy treatment, he said.

Limited need for surgery

Surgery to treat HO is done infrequently, according to Bajwa and Hoffmeyer, who noted this may be because prevention and early detection, before HO affects an individual’s mobility and function, has improved greatly.

Hoffmeyer cited data on THR revisions performed for HO in the latest Australian National Joint Replacement Registry to make his case about how few such procedures are performed. Of the 17,000 cases of THR revision for HO in the registry performed between September 1999 and December 2014, “[there were] 20 cases of primary hips that needed revision for heterotopic bone,” Hoffmeyer said.

“It is not a huge problem,” he said, explaining a heavy, athletic man, such as a soccer player, who undergoes THR may develop Brooker grade 2 or 3 HO. Unless that patient is sore or has pain, Hoffmeyer will not revise him or her.

TDA revisions

Occasionally, HO will result in narrowing of the neuroforamen and will need to be revised, Mehren said. Clinically, HO in TDA is more of a radiographic problem detectable on lateral radiographs and it has no clinical impact, he said.

Furthermore, CT is not needed to detect HO in these cases, Mehren noted.

Mehren and colleagues studied rates of HO in TDA through 10-years follow-up. By including and describing every small ossification in those cases, they saw HO rates of 10% at 1 year increase to 25% to 30% at 5 years and to 50% at 10 years.

“Of course, it is increasing over time,” Mehren said.

Mehren always informs his patients they have radiographic HO, but also tells them not to worry about the problem because it usually is not associated with any symptoms or pain for which treatment is indicated.

Uncommon in knee, shoulder replacement

Hoffmeyer said HO is rare in knee replacement surgery because there is less muscle in the knee and more tendons. It has been reported around the shoulder following total shoulder arthroplasty (TSA), particularly 20 years to 30 years ago. He said, aside from a few clouds that appeared on radiographs, he has never seen it in any TSAs he has performed.

As for the future of HO management, Bajwa said patients who are positive for HLAB27 and have ankylosing spondylitis, for example, are likely to develop HO. Therefore, sophisticated genetic screens to see which patients are likely to get HO might prove helpful.

“Ideally, we should have [markers] we can check, but they are still not cost-effective,” Bajwa said, and HO is no longer a big enough problem to warrant general genetic testing, he noted. – by Susan M. Rapp

Disclosures: Bajwa, Curt, Hoffmeyer, Mehren and Weidner report no relevant financial disclosures.