Heterotopic Ossification After Arthroscopy for Hip Impingement Syndrome

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Heterotopic Ossification After Arthroscopy for Hip Impingement Syndrome: What You Need to Know

If you or someone you know has undergone hip arthroscopy for femoroacetabular impingement (FAI)—a common cause of hip pain where the femur and acetabulum rub together—you may have heard of heterotopic ossification (HO). HO is a complication where bone forms in non-skeletal tissues like muscles or joint capsules, potentially causing pain or limited movement. A 2019 study from Peking University Third Hospital offers critical insights into how often HO occurs after this procedure, who might need additional surgery, and what outcomes to expect.

What the Study Examined

Led by researchers at the Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, the retrospective study followed 242 patients (140 men, 102 women; average age 36.2 years) who had hip arthroscopy for FAI between January 2016 and January 2018. The team tracked patients for an average of 22.88 months (range: 11–34 months) to:

  1. Calculate the incidence of HO after surgery.
  2. Compare pain and function in patients with and without HO.
  3. Evaluate whether removing HO (revision surgery) improved outcomes for those with persistent symptoms.

Patients were excluded if they had HO before surgery. No one received HO prevention treatment (e.g., NSAIDs) initially—though four patients who later had revision surgery took 60mg of etoricoxib daily for six weeks afterward.

How They Measured Success

The team used three key tools to assess hip health:

  • Visual Analog Scale (VAS): Ranks pain from 1 (painless) to 10 (worst possible).
  • Modified Harris Hip Score (mHHS): Measures hip function (e.g., walking, climbing stairs) on a 100-point scale.
  • Non-Arthritis Hip Score (NAHS): Evaluates pain and function specifically for people without arthritis.

HO severity was graded using the Brooker classification, a four-stage system:

  • Stage I: Tiny, isolated bone islands.
  • Stage II: Bone spurs with >1cm of space between bones.
  • Stage III: Bone spurs with <1cm of space.
  • Stage IV: Complete joint fusion.

What They Found

Of the 242 patients:

  • 5.4% developed HO (13 total: 6 men, 7 women; average age 37.5 years).
  • Most HO was mild: 9 cases (69%) were Stage I, 3 (23%) Stage II, 1 (8%) Stage III. No one had Stage IV.
  • 10 of 13 patients with HO had no major symptoms: Their pain (VAS) and function (mHHS, NAHS) scores were similar to patients without HO.
  • 4 patients needed revision surgery: They had persistent pain that didn’t improve with physical therapy, activity changes, or anti-inflammatories for at least three months. After HO removal:
    • Pain dropped dramatically (VAS from 5.5 to 1.5).
    • Function soared: mHHS jumped from 53.75 to 88.5; NAHS from 51.75 to 80.5.
    • All four reported high satisfaction (average score: 8.46/10).

Why This Matters for Hip Arthroscopy Patients

  1. HO is rare after arthroscopy: The 5.4% incidence is far lower than the 37% seen in open hip surgery for FAI. Researchers think this is because arthroscopy causes less trauma, bleeding, and bone debris—all triggers for HO.
  2. Most HO doesn’t need treatment: Only 30% of patients with HO (4/13) required surgery. For most, HO is a “silent” complication that doesn’t affect daily life.
  3. Ultrasound is key for early detection: The study used ultrasound to spot HO as early as three weeks post-surgery—far sooner than X-rays or CT scans, which only detect mature bone. Ultrasound is also radiation-free, cheap, and portable—great for follow-ups.
  4. NSAIDs can prevent HO: Past studies (like one from Beckmann et al. in 2016) found naproxen reduced HO risk from 46% to 4% in hip arthroscopy patients. The Peking team noted that patients who had revision surgery took NSAIDs afterward to prevent recurrence.

Limitations to Keep in Mind

  • Retrospective design: The study looked back at existing data, which can introduce bias (e.g., missing records).
  • Ultrasound expertise required: Only doctors with 10+ years of musculoskeletal experience could perform the scans—most orthopedic surgeons can’t do this independently.
  • Small revision sample: Only four patients had HO removal, so results for this group are based on a tiny number.

Key Takeaways

If you’re considering or recovering from hip arthroscopy for FAI:

  • Don’t panic about HO: It’s uncommon, and most cases are mild.
  • Ask about ultrasound follow-ups: It’s the best way to catch early HO.
  • Talk to your doctor about NSAIDs: If you’re at high risk for HO (e.g., previous bone issues), prophylaxis might help.
  • Revision surgery works if you need it: If pain persists for months, removing HO can drastically improve your quality of life.

This study was published in the Chinese Medical Journal in 2019 by Guan-Ying Gao, Xin Zhang, Ling-Hui Dai, Hong-Jie Huang, Rui-Qi Wu, Xiao-Dong Ju, Yu Mei, Xing-Yue Niu, Jian-Quan Wang, and Yan Xu from the Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital.

doi.org/10.1097/CM9.0000000000000153

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