Chest wall heterotopic ossification causing restrictive physiology after resuscitative thoracotomy and surgical stabilization of rib fractures: a report and review

Case presentation

An adult male in his 60s underwent resuscitative thoracotomy for blunt traumatic arrest after a motorcycle crash. He subsequently underwent surgical stabilization of rib fractures (SSRF) to stabilize the flail chest present at the time of resuscitative thoracotomy, and additional rib fractures sustained during Finochietto placement. He presented 12 months post injury with persistent dyspnea and a restrictive sensation in his left chest. Pulmonary function tests (PFTs) demonstrated extrinsic restrictive pulmonary physiology (table 1). Subsequent CT chest with intravenous contrast demonstrated heterotopic ossification (HO) of his left chest wall involving the previously placed extrathoracic titanium implants with unicortical screw fixation (figure 1).

Table 1. Pulmonary function testing obtained preoperatively and postoperatively, respectively, demonstrating extrinsic restrictive pulmonary physiology and a subsequent improvement in the FEV₁/FVC ratio.

	5 months preoperatively	6 weeks postoperatively
FVC (L) (% predicted)	3.04 (69%)	2.67 (61%)
FEV1 (L) (% predicted)	2.09 (62%)	1.93 (58%)
FEV1/FVC (% predicted)	69 (89%)	76 (94%)
TLC (L)	4.96	4.37
DLCO (% predicted)	30.2 (113%)	24.9 (94%)

DLCO, diffusing lung capacity for carbon monoxide; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; TLC, total lung capacity.

Figure 1. Non-contrast CT imaging of the chest with 3D reconstructions obtained 13 months post injury and surgical stabilization of rib fractures demonstrating significant heterotopic ossification of the left chest wall with hardware involvement, corresponding to the patient’s previous rib fractures: (A) a representative sagittal slice of intercostal bridging calcifications of left lateral ribs; (B) 3D reconstruction of the chest wall demonstrating intact extrathoracic titanium plates (red) with intercostal bridging calcifications of the left lateral ribs 1 to 8; (C) 3D reconstruction of the chest wall demonstrating intact extrathoracic titanium plates (red) with intercostal bridging calcifications of left posterior ribs 4–9.

What would you do?

1. Ongoing physical therapy and pulmonary rehabilitation.

2. Focused chest wall radiation therapy only.

3. Focused chest wall radiation therapy plus indomethacin.

4. Surgical excision of HO only.

5. Surgical excision of HO with concomitant hardware removal.

6. C and E.

What we did and why

Given the symptomatic and anatomic extent of the patient’s HO, we chose a multimodal treatment strategy. The patient underwent complete excision of his left chest wall HO with concomitant implant removal. The day before surgery, he received focused radiation therapy with delivery of 7 Gy in one fraction to his left chest wall using intensity-modulated radiation therapy (IMRT) with the RefleXion X1 machine (RefleXion Medical, Hayward, CA, USA) (figure 2). Intraoperatively, we completely excised the extensive HO between left ribs 3 to 7 with implant removal. Notably, two stripped screws could not be removed and thus remained in situ to avoid additional bone and soft tissue injury from repeated manipulation.

Figure 2. CT simulation of the chest with representative transverse, Beam’s Eye View, coronal, and sagittal projections with overlaid isodose distributions from the delivered intensity-modulated radiation therapy treatment plan for prophylactic prevention of heterotopic ossification.

The patient experienced immediate symptomatic relief postoperatively. He was discharged home on postoperative day 4 on a 30-day course of indomethacin (25 mg by mouth three times per day) in addition to a standard multimodal analgesic regimen. Repeat PFTs at 6 weeks postoperatively demonstrated an interval improvement in his forced expiratory volume in one second (FEV₁) to forced vital capacity (FVC) ratio (FEV₁/FVC) (table 1). The 3-month postoperative imaging did not demonstrate any recurrent HO. By 4 months, his pain and restrictive sensation had both substantially improved.

Discussion

HO remains a rare but debilitating sequela of severe chest wall trauma and SSRF. However, chest wall HO is rarely reported and thus lacks standardized management.¹,⁴ Our patient developed symptomatic mature HO of the chest wall 1 year after resuscitative thoracotomy and SSRF that manifested as extrinsic restrictive pulmonary physiology. We suspect its etiology was multifactorial and due to the severe primary musculoskeletal trauma sustained in the motorcycle crash, secondary trauma sustained during resuscitative thoracotomy, and additional tissue dissection required during eventual SSRF.

This case provides additional evidence that surgical excision is an effective and safe treatment modality for intercostal HO and should be considered for appropriately selected patients. Complete HO excision and implant removal led to both subjective and objective improvements in our patient’s respiratory status, as respectively evidenced by his symptom resolution and increased FEV₁/FVC ratio. As postoperative testing occurred at 6 weeks, absolute volumes may underestimate longer-term recovery, which subjectively continued over subsequent months. Given the patient’s ongoing clinical improvement, repeat PFTs were not performed. This supports existing anecdotal evidence that complete surgical excision of mature HO is associated with decreased recurrence rates compared with partial excision.⁵

Several non-surgical adjuncts have been described to help reduce HO development in high-risk patients. Potentially modifiable contributors include minimizing soft tissue disruption, obtaining meticulous hemostasis, and appropriately tailoring administration of prophylactic therapies. Non-selective non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed postoperatively to reduce inflammation and limit abnormal bone formation. Selective cyclooxygenase-2 inhibitors are similarly effective in preventing HO and tout fewer gastrointestinal side effects than non-selective NSAIDs, although long-term use may carry cardiovascular risks.⁶ Although these means may prevent progression or recurrence of HO, mature symptomatic HO often requires complete surgical excision. Low-dose radiation therapy may be combined with surgical excision to minimize recurrence risk and is typically delivered as a single fraction either within 24 hours preoperatively or 72 hours postoperatively.^{7 8}

Currently, there are limited evidence-based recommendations to guide chest wall HO management, with most of the available data stemming from either case reports or case series. This underscores the need for further definition of optimal prevention and treatment strategies, as well as appropriate surgical timing when indicated.

Clinicians should consider HO as a possible long-term complication in patients with severe thoracic trauma or operative chest wall exposure who present with persistent or recurrent chest wall discomfort, respiratory dysfunction, or functional limitation weeks to months after injury or surgery. Markers of severe injury such as prolonged mechanical ventilation, Intensive Care Unit (ICU) admission, and/or multiple rib fractures are associated with HO in other trauma populations.^{4 9} However, chest wall-specific predictors remain poorly defined and warrant further investigation. Early identification and appropriate referral for surgical evaluation may improve long-term outcomes and quality of life for this unique patient population.