MSK Complications, Functional Outcomes, and the Rehabilitation Continuum
SCI · EP 14 · NEUROREHAB
Before You Listen
- Prerequisites: spinal cord neuroanatomy and the American Spinal Injury Association Impairment Scale (AIS) from SCI-01 and SCI-03; pressure injury prevention and the Braden Scale from SCI-12; autonomic dysreflexia (AD) physiology from SCI-05; basic musculoskeletal anatomy and orthopedic principles.
- Runtime: 1 hour 18 minutes.
- Topic in one line: heterotopic ossification (HO) of the hip with alkaline phosphatase (ALP) as the earliest lab and triple-phase bone scan as the most sensitive early imaging; sublesional osteoporosis at the distal femur and proximal tibia; fragility fractures that present painlessly and the prohibition on circumferential casts; carpal tunnel syndrome (CTS) in 40 to 66 percent of manual wheelchair users; the functional outcomes table with C6 as the highest level for independent living and C7 as the usual level for independence; the tenodesis grasp and the therapeutic error of overstretching the flexor tendons; the orthotic ladder of knee-ankle-foot orthosis (KAFO) to ankle-foot orthosis (AFO); the Functional Independence Measure (FIM) and its ceiling effect; concurrent traumatic brain injury (TBI) in 25 to 60 percent; cervical spondylotic myelopathy as the most common nontraumatic cause; and transverse myelitis with the lesion-length distinction.
Vignette. A 32-year-old man with C6 motor-complete tetraplegia (AIS A) is 6 weeks post-injury and medically stable. His admission FIM is 38; today his FIM is 64. The team is preparing him for discharge. His mother asks whether he will walk again, whether he can live alone, what equipment he needs, and what changes the family must make to the house. On exam, his elbow flexes against gravity (biceps), his wrist extends against gravity (extensor carpi radialis), and his triceps test 0 of 5. Sensation is intact to the C6 dermatome and absent below.
Based on his injury level, what realistic functional outcomes should you describe for activities of daily living (ADLs), mobility, and transfers? What rehabilitation principle is most easily violated by a well-meaning therapist or family caregiver? What equipment will he need? What housing modifications are essential? Will he walk?
Section 1: Heterotopic Ossification
Bottom line: HO is mature lamellar bone forming in periarticular soft tissues below the level of injury, occurring in 16 to 53 percent of SCI patients with the hip in 70 to 80 percent. Onset is 1 to 4 months post-injury (peak at 2). Alkaline phosphatase rises first (2 to 3 weeks before symptoms); triple-phase bone scan is the most sensitive early imaging (positive 2 to 4 weeks before X-ray); plain films lag at 4 to 6 weeks. Surgical excision waits 12 to 18 months until the bone is mature (cold bone scan). Always exclude DVT first.
Heterotopic ossification (HO) is the formation of mature lamellar bone within periarticular soft tissues in locations where bone does not normally exist. It occurs exclusively below the neurologic level of injury. Pathogenesis involves aberrant differentiation of mesenchymal stem cells into osteoblastic lineages, driven by local inflammatory mediators, altered vascular permeability, loss of sympathetic regulation of bone metabolism, circulating osteogenic growth factors, and venous stasis.
Incidence is 16 to 53 percent. The anatomic distribution is heavily tested: the hip accounts for 70 to 80 percent of cases, followed by the knee, then the shoulder, then the elbow. HO is invariably periarticular. Onset is 1 to 4 months post-injury, peaking at approximately 2 months.
The strongest risk factor is complete injury (AIS A). Other risk factors: spasticity (microtrauma from involuntary contractions), active pelvic pressure injuries, recurrent urinary tract infections, deep vein thrombosis (DVT, which shares risk factors with HO and frequently coexists), and overly aggressive passive range of motion. Well-intentioned forceful joint mobilization by therapists or family caregivers can produce the very microtrauma that promotes HO. Gentle range of motion is therapeutic; aggressive stretching is counterproductive.
The clinical presentation is swelling, warmth, erythema, and decreased range of motion, sometimes with low-grade fever. This closely mimics DVT, and the two share risk factors and can coexist. DVT must be excluded with duplex ultrasound first before symptoms are attributed to HO.
Serum alkaline phosphatase (ALP) is the earliest laboratory marker, reflecting increased osteoblastic activity. ALP begins rising approximately 2 to 3 weeks before clinical or radiographic signs, peaks around 10 weeks, and typically normalizes by 6 to 12 months. ALP is nonspecific, but serial trending in an SCI patient at 1 to 4 months post-injury is a reliable early-warning system.
Triple-phase bone scan with technetium-99m methylene diphosphonate is the most sensitive early imaging study. All three phases (flow, blood pool, delayed) are positive in active HO. The bone scan turns positive 2 to 4 weeks before plain radiographic changes. Plain radiographs are a lagging indicator, becoming positive only 4 to 6 weeks after clinical onset. CT provides superior anatomic detail for surgical planning.
Treatment begins with gentle range of motion, avoiding aggressive stretching. Pharmacologic options include etidronate disodium, a first-generation bisphosphonate that inhibits mineralization of the osteoid matrix (it does not prevent osteoid formation). Typical dosing: 20 mg/kg/day for 2 weeks then 10 mg/kg/day for 10 weeks. Indomethacin 25 mg TID for 3 to 6 weeks inhibits prostaglandin-mediated bone formation and is used for prophylaxis.
Surgical excision is indicated when HO significantly restricts ROM, impairs sitting, transfers, or positioning, causes skin breakdown, or compresses neurovascular structures. The critical timing principle: delay surgery until HO has matured, typically 12 to 18 months after onset. Premature excision carries high recurrence risk because biological signals are still active. Maturity is best confirmed by a cold bone scan; ALP correlates poorly with bone activity and should not be the sole maturity indicator. Perioperative prophylaxis with indomethacin, radiation, or etidronate may reduce recurrence.
Board Trap: HO vs DVT
A swollen, warm extremity in an SCI patient 2 months after injury could be HO or DVT or both. Always exclude DVT with duplex ultrasound first. Then check ALP and consider triple-phase bone scan for HO. Treatment is opposite: DVT requires anticoagulation; HO requires range of motion plus NSAID or bisphosphonate. The two conditions can coexist.
High Yield: Heterotopic Ossification
- HO incidence: 16 to 53 percent; hip 70 to 80 percent (most common); knee, shoulder, elbow follow.
- Onset: 1 to 4 months post-injury (peak at 2 months); always below the level of injury.
- ALP is the earliest lab marker; triple-phase bone scan is the most sensitive early imaging.
- Plain X-ray lags at 4 to 6 weeks.
- Indomethacin 25 mg TID for 3 to 6 weeks for prophylaxis; etidronate 20 mg/kg/day for 2 weeks then 10 mg/kg/day for 10 weeks.
- Surgical excision delayed to 12 to 18 months until cold bone scan confirms maturity.
- HO mimics DVT; always exclude DVT first with duplex ultrasound.
So if a therapist aggressively stretches those fingers into full extension while the wrist is also extended, they physically elongate those tendons. The tenodesis grasp is just gone. Weakened or completely eliminated. And you cannot get it back.
— SCI-14 podcast, ~02:43