Tag Archive | HO

Histology Yields Clues to HO in Injured Service Members

HO Mineral Apposition.gifBetween 2000 and 2014, 1573 wounded US service members sustained one or more major amputations, and nearly two-thirds of those individuals developed posttraumatic heterotopic ossification (HO). Deciding when to excise HO (which can cause pain and interfere with rehabilitation programs and prosthetic limbs) requires careful consideration, and findings from a study by Isaacson et al. in the April 20, 2016 JBJS may help surgeons and patients faced with that decision.

Using sophisticated microscopy techniques to analyze symptomatic heterotopic bone excised from 33 service members following combat-related trauma, Isaacson et al. determined that mineral apposition rates in the HO specimens averaged 1.7 μm/day, which is 1.7 times higher than the 1.0 μm/day rate typically found in non-pathological human bone. The authors also found a direct relationship between mineral apposition rates and clinical predictors of HO, such as traumatic brain injury. The findings further suggested that mineral apposition rates correlate with the severity of HO recurrence.

Although the mineral apposition rates increased along with the time from injury to excision, the authors concluded that “the optimal time to resect symptomatic HO must still be a clinical decision,” and they call for further investigation into correlations between mineral apposition rates and HO development and recurrence.

Naproxen Effective for Preventing HO after Hip Arthroscopy

Heterotopic ossification (HO) is a known complication of hip arthroplasty. A double-blF6.medium (2)ind, randomized, placebo-controlled trial by Beckmann et al. in the December 16, 2015 Journal of Bone & Joint Surgery showed that prophylaxis with naproxen dramatically reduced the prevalence of HO after hip arthroscopy, without serious medication-related side effects. These findings bolster findings from previous retrospective investigations that showed large reductions in HO prevalence among those taking nonsteroidal anti-inflammatory drugs (NSAIDs).

The patients in the study took naproxen (500 mg) or a placebo twice a day for three weeks following arthroscopic surgery for femoroacetabular impingement.  After one year, the prevalence of radiographically determined HO in patients randomized to the naproxen group was 4% versus 46% in the patients randomized to the placebo group, an 11-fold difference. While the potential for serious GI and renal side effects with NSAIDs is well-documented, in this study only minor adverse reactions to study medication were reported in 42% of those taking naproxen and in 35% of those taking placebo.

Noting that the clinical consequences of HO following hip arthroscopy are “largely undetermined,” the authors still suggest a role for HO prophylaxis “because it could reduce the risk of developing symptomatic HO or requiring revision surgery for HO excision.”

In an accompanying commentary, Sverre Loken praises the authors for the well-designed study, but he cautions that “clinically relevant HO is uncommon, and this has to be weighed against the risk of serious side effects caused by NSAIDs.” He also emphasizes the observation Beckmann et al. make in the last paragraph of their study: that “the lowest dose and shortest duration of NSAID prophylaxis that still prevent HO remain to be determined.”