Spondylolysis

Spondylolysis is a defect or stress fracture of the pars interarticularis, the part of the vertebral arch between the superior and inferior articular processes. It is the commonest identifiable cause of low back pain in adolescent athletes, and affects the fifth lumbar vertebra in 85 to 90% of cases and the fourth in most of the rest.

The prevalence is about 4 to 6% in the general population (with the first defects appearing at 5 to 7 years of age), and up to 40 to 47% of adolescent athletes with back pain have it. It is about twice as common in males, and bilateral in 60 to 80%. Sports with repeated lumbar extension and rotation carry the highest risk: gymnastics, diving, cricket fast bowling, American style football, weightlifting, rowing, dance and wrestling. A family history and spina bifida occulta raise the risk.

Most heal with rest and rehabilitation in the early stage. In 15 to 20% of bilateral defects the vertebra slips forward (isthmic spondylolisthesis). Complications are chronic pain, non-union, slippage, radiculopathy, and loss of sporting activity.

Pathophysiology.

Repeated hyperextension and rotation concentrate load at the pars, which causes a stress reaction, then an incomplete fatigue fracture, and finally a fibrous non-union. Genetic susceptibility, a lordotic upright posture, tight hamstrings and a thin pars contribute. The defect is an acquired stress fracture, not a congenital one.

Insidious central or unilateral low back pain that increases with extension, running, jumping and twisting and settles with rest, often for weeks to months. Leg pain is unusual, and neurological signs are rare unless slippage occurs.

Examine the single leg hyperextension (stork) test, which reproduces pain on the side of the defect, paraspinal spasm, tenderness over the affected level, tight hamstrings, increased lumbar lordosis, forward flexion, and neurological state (power, reflexes, sensation, straight leg raise). A palpable step suggests a slip.

• Standing anteroposterior, lateral and oblique radiographs: a defect in the neck of the "Scottie dog" on the oblique view, with a lateral view to exclude a slip. Radiographs miss up to 20 to 30% of early lesions.
• MRI (no radiation) is the preferred first investigation in children: shows bone marrow oedema in the pars in the early stage, and the fracture line.
• SPECT bone scan is very sensitive for active lesions when MRI is not available.
• Thin slice CT with limited radiation stages the lesion (early, progressive, terminal) and shows healing; used when it will change management.
• Blood tests: 25-hydroxyvitamin D, calcium and phosphate; assess calorie intake, menstrual history and bone health in female athletes (the female athlete triad).

Differential diagnosis.

• Lumbar muscle strain and discogenic pain.
• Facet joint pain, sacroiliac joint dysfunction and Scheuermann disease.
• Stress fracture of the pedicle, sacrum or lamina.
• Osteoid osteoma, infection and tumour.

The aim is to heal the lesion when possible, control pain and return to sport safely. About 70 to 90% of early unilateral lesions unite, while terminal, bilateral lesions rarely do but can still become asymptomatic.

Activity and rehabilitation.

• Rest from the provoking sport for 3 months (and until pain free for at least 4 weeks), with continued daily activity and low load exercise.
• An anti-lordotic thoracolumbosacral brace worn for up to 23 hours a day for 3 to 6 months is used in some centres for early lesions; pain outcomes match those of activity restriction alone, and the brace is used when compliance with rest is poor.
• Physiotherapy: core and lumbopelvic stabilisation, hamstring and hip flexor stretching, and sport specific retraining, begun once the pain settles; graded return to sport at 3 to 6 months, based on pain free function, and where possible on imaging showing healing.

Medication.

• Paracetamol 15 mg/kg orally every 4 to 6 hours as needed (maximum 75 mg/kg daily and not exceeding 4 g daily); adolescents of 50 kg or more: 1 g every 6 hours (maximum 4 g daily).
• Ibuprofen 10 mg/kg orally every 6 to 8 hours with food (maximum 40 mg/kg daily and not exceeding 2400 mg daily; adolescents 400 mg every 8 hours) limited to 5 days, since prolonged use may impair bone healing.
• Avoid ibuprofen with kidney impairment, dehydration, asthma sensitive to NSAIDs or active bleeding.
• Vitamin D deficiency (25-hydroxyvitamin D under 30 nmol/L): colecalciferol 50 000 units orally once weekly for 6 to 8 weeks, then 1000 to 2000 units daily; ensure calcium intake of 1300 mg daily at 9 to 18 years.

Surgery (persistent disabling pain after 6 to 12 months of well supervised non-operative treatment).

• Direct repair of the pars with bone graft and fixation (pedicle screw and rod, pedicle screw with hook, or a tension band wire) for lesions at L4 or L5 in patients with a preserved disc and no slip; union in 80 to 90%.
• Fusion (the affected level with one adjacent level) for a slip, degenerate disc, or failed repair.
• After surgery, a brace for 3 months and return to sport at 6 to 9 months once union is shown.

Operative antibiotic prophylaxis. Cefazolin 30 mg/kg to a maximum of 2 g intravenously (2 g in adolescents and adults; 3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose (repeat after 4 hours or blood loss over 1500 mL).

With severe penicillin allergy, use clindamycin 10 mg/kg (maximum 900 mg) intravenously or vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose.

Analgesia after surgery. Paracetamol 15 mg/kg orally every 4 to 6 hours (maximum 75 mg/kg daily and not exceeding 4 g daily).

Oral morphine 0.1 to 0.2 mg/kg every 4 hours as needed for up to 3 days (maximum 10 mg a dose); monitor sedation and respiration; prescribe a laxative.

Monitoring. Review at 6 weeks and 3 months to check pain, then follow up imaging (MRI or low dose CT) at 3 to 6 months if the plan is to resume sport. Watch for a slip with standing lateral radiographs at 6 and 12 months in bilateral lesions, and every 6 to 12 months to skeletal maturity in children with a slip. Bone health and nutrition in female athletes.

Referral and escalation. Refer an adolescent with back pain lasting over 4 to 6 weeks, or with pain that increases on extension, to a sports medicine or spinal service. Urgent referral for neurological signs, a slip over 25 to 50%, night pain, fever or weight loss.

Special groups.

• Elite young athletes: remove the cause (technique, training volume), check for stress injury in other bones, and adjust the sport schedule.
• Children under 10 years: usually a defect found by chance; observe.
• Female athletes: screen for low energy availability, amenorrhoea and low bone density.
• Adults with persistent symptoms: physiotherapy and image directed injections; fusion for a slip or failure.