Surgical resection of HO post SCI is a well established treatment but still somewhat controversial.
A case control study by Hollenberg and Mesfin (2020) assessed the influence of traumatic SCI on the operative management of cervical ossification of the posterior longitudinal ligament (OPLL). A chart review of the medical records of 12 individuals with SCI and 16 individuals with cervical myelopathy (CM) who underwent surgical management for OPLL was performed. It was found that while most patients in both the SCI with OPLL group and the CM with OPLL group showed neurologic improvement after the surgery, patients with SCI had worse postoperative neurologic motor scores compared to those with CM.
The timing for surgical resection continues to split consensus with surgery being conducted once the ectopic bone has completely matured being considered the usual course of action. Despite that, there are growing calls for surgery to be delayed until the patient has fully recovered from their SCI (Gurcan et al. 2013). However, a delay in excision has been found to lead to a series of negative events such as increased risk of fracture, ankylosis, bone loss, and intra-articular lesions (Genêt et al. 2015).
Meiners et al. (1997) reported a case series of 29 individuals (10 with quadriplegia and 19 with paraplegia) who underwent HO resection at the hip followed by irradiation and eventually passive range of motion exercises. Mean hip range of motion increased from 21.95º pre-operatively to 94.51º intra-operatively and 82.68º at four year (mean) follow-up. Garland and Orwin (1989) also reported that HO excision improves range of motion in 19 individuals with SCI. They found that the largest gain of function occurred intra-operatively followed by a large loss of function within the first six months. At final follow-up (six years post-surgery), three of 24 hip joints where HO was surgically excised had similar or less motion when compared with preoperative motion, 15 improved between 10° and 39°, while six showed greater than 40° improvement.Yang et al. (2017) found similar rates of improvement following HO resection. In a case series with eight patients that underwent surgical resection, six healed well, one patient had ongoing healing at 6 months due to a post-operative infection, and one patient died (Yang et al. 2017).
Some studies stress that surgical resection must be followed up by prophylaxis, either radiation therapy, NSAID or bisphosphonates due to high recurrence rates after surgery alone. A case study by Gurcan et al. (2013) investigated the use of surgical resection in a patient with total ankylosis of the right hip following a T8-T9 fracture. Upon excision of the cephalad mass, the patient’s hip could be flexed to 100o and abducted to 30o on the operating table, indicating a successful operation. At post-surgery, the patient completed passive movements of the hip, and was treated with a single dose of radiation (eight Gy) and a prescription for indomethacin with a dosage of 150mg a day. At 12-month follow-up post-surgery, the range of motion in the hip remained preserved with no recurrence of HO or ankylosis.
The effectiveness of surgical excision followed by bisphosphonates was examined in two case series (Schuetz et al. 2005; Subbarao et al. 1987). Etidronate treatment post-surgical excision showed that patients were able to function independently in a wheelchair; however, they had severe restrictions in their range of motion (Subbarao et al. (1987). Surgical excision supplemented with pamidronate treatment resulted in no recurrence of HO post-surgery (Schuetz et al. 2005).
Genêt et al. (2015) conducted a review of the literature regarding recurrence rates of HO after surgical excision. A finding of concern was the lack of consensus towards the classification of HO and risk of recurrence and whilst some studies have attempted, the authors point out that these are based on observations and are merely descriptive. Moreover, the review was not able to clarify ideal timing for surgical resection, in part due to disparate rates of recurrence post-surgery. A prominent issue of HO recurrence is the definition of recurrence. Genêt et al. (2015) highlight that some patients are not deemed to have had recurring HO post-surgery if the patient’s functioning is not impaired, and adds that pre- and post-surgical care are not standardized with early rehabilitation such as limb mobilization often being delayed due to inflammation and treated with NSAIDs instead.
There is level 3 evidence (from one case control study; Hollenberg & Mesfin, 2020) that patients with SCI complicated by OPLL may have worse preoperative and postoperative motor function compared to patients with CM and OPLL.
There is level 4 evidence (from four case series: Garland & Orwin 1989; Meiners et al. 1997; Genet et al. 2011; Yang et al. 2017) that resection of HO about the hip post SCI can dramatically improve restricted hip range of motion; however, post-surgical recurrence and complications are a concern for this treatment.
There is Level 4 evidence (from one case series: Schuetz et al. 2005) that surgical resection combined with pamidronate treatment effectively halts secondary HO progression.
There is level 4 evidence (from one case series: Subbarao et al. 1987) that surgical resection combined with etidronate treatment improves independence with wheelchair use but contributes to reduced range of motion.