1. Jennifer S. Coulter, DO; Thomas S Kiser, MD, MPH
Inpatient Rehabilitation for Thoracic Myelopathy Caused By X-Linked Hypophosphatemia, a Form of Congenital Rickets, After Surgical Decompression and Fusion: A Case Report.
Jennifer S. Coulter, DO; Thomas S Kiser, MD, MPH
Department of Physical Medicine and Rehabilitation, University of Arkansas for Medical Sciences, Little Rock, AR
ABSTRACT
DISCUSSION
IMAGING
A 56 year-old woman with X-Linked Hypophosphatemia (XLH), a form of congenital rickets that causes renal phosphate wasting and affects bone mineralization, had a history of more than 30 orthopedic surgeries to manage progressive bone deformities and spinal stenosis. Despite these problems, she was able to maintain an independent lifestyle. She used a power wheelchair for mobility for the last 12 years due to declining mobility and drove a van with hand controls and a wheelchair lift. A year prior to admission she developed intractable back pain causing her to stop driving, and her transfers deteriorated to the point that she required total assistance to transfer. She had to discontinue her favorite pastime of swimming. In an attempt to alleviate the pain that immobilized her she went on a starvation diet to lose weight, but despite losing 120 lbs she was no better. An MRI of her spine was not impressive for new pathology, but further workup with a thoracic and lumbar CT myelogram showed severe right foraminal narrowing at T4-5, T5-6, T6-7, T9-10, and T10-T11, with hardware loosening at T4 and severe bilateral facet arthropathy causing posterior deviation of the spinal cord with bilateral T6-7 foraminal narrowing. She subsequently underwent a posterior decompression of T6-7 and reinstrumentation and fusion of T2-T8. She was then transferred to inpatient rehabilitation to address her functional deficits. She showed rapid neurologic benefit from the decompression surgery from day one. She was able stand and transfer and could not contain her tears of joy. She then advanced to ambulation in the parallel bars, which was the first time she walked in 12 years. By discharge, she was able to walk 8 feet and continued to improve with outpatient therapy to 75 feet with a rolling walker by her first orthopedic follow up.
X-Linked Hypophosphatemia is an inherited mutation of the X-linked phosphate-regulating endopeptidase homolog (PHEX) genes, causing a decrease in the fibroblast growth factor 23 (FGF23) protein. This leads to decreased reabsorption of phosphate at the kidneys and decreased 1,25-OH vitamin D production. There is phosphate wasting in the urine and altered phosphate availability to the skeleton, causing decreased mineralization of long bones. Patients with this disorder present in childhood with short stature and bowing of the legs at the time of weight bearing. Even after skeletal maturity, patients may have continued degeneration and deformities of the knees, hips, and ligaments, altering gait mechanics. Ligamentum flavum hypertrophy and spine ossification can cause spinal or neural foraminal stenosis, leading to pain, bowel/bladder dysfunction, weakness, or paresthesias.
Medical treatment includes frequent lab monitoring and oral phosphate and calcitriol. There is risk of vitamin D toxicity and hypercalcemia, particularly while the patient has limited mobility during post-op recovery periods. Surgical management is case dependent and include osteotomies, femoral lengthening with intramedullary nails, and surgical decompression of the spine.
Figure 2: Axial slice on CT Myelogram through the T5-6 foramina showing right sided sclerosis and facet joint hypertrophy causing severe compression of the exiting nerve root.
Figure 1: Sagittal image on CT Myelogram of the thoracic spine in bone window showing severe stenosis at the level of the right T5-T6 neural foramina
CONCLUSIONS
Patients with XLH have lifelong issues of bone mineralization and mechanical axis deviations. They usually undergo multiple surgeries in their lifetime in attempts to correct bony deformities, maximize height, improve function, and reduce pain.
It is important for the rehab physician to be aware of the disease process, the risks and benefits of surgical management, and the medical supplementation needs of the patient during recovery after surgery. Extra care must be taken to avoid fractures and falls, which may hinder recovery and mobility.
CLINICAL COURSE
During her acute inpatient rehabilitation stay, she was ambulating 8 feet with parallel bars, though with knee instability. The patient’s endocrinologist was contacted to discuss medications (phosphorous and calcitriol) as well as her chronic creatinine elevation.
At the peak of her recovery months later, she was able to ambulate 210 feet with a rolling walker. She had resumed swimming. Unfortunately, she developed a stress fracture on her right femur and worsened arthritic pain of her left wrist when using the walker, and has decreased her ambulation due to risk of fractures and falls. She is still able to transfer and perform her ADLs with modified independence, which has greatly improved her quality of life.
Figure 4: Coronal view on CT Myelogram revealing a moderate sized pseudomeningocele at the level of left T7-8 exit foramina compromising the foraminal lumen.
REFERENCES
Figure 3: Axial image on CT Myelogram at the the L5-S1 level showing compromise on the right side secondary to facet joint hypertrophy and a large foraminal osteophyte.
Sharkey M, Grunseich K, Carpenter T. Contemporary medical and surgical management of x-linked hypophosphatemic rickets. J Am Acad Orthop Surg. 2015;23(7):
Riccio A, Entezami P, Giuffrida A, Dowling J, Forrest G, German J. Minimally invasive surgical management of thoracic ossification of the ligamentum flavum associated with x-linked hypophosphatemia. World Neurosurg. 2016;94:580.e5-580.e10.