A pars interarticularis injury (also known as a “pars injury”) is a condition that is commonly seen in young athletes who participate in sports requiring them to repetitively lean backwards, such as ballet, gymnastics or cricket.
This condition affects an area of the spine called the pars interarticularis. The pars interarticularis is a small segment of bone that joins the superior and inferior facet joints of the spine. This can happen on one side (unilateral) or on both sides (bilateral) of the spine.
What causes a Pars Injury
A pars injury is often caused from overuse or over training in sports that demand repetitive hyperextension and/or rotation of the lumbar spine. Repetitive hyperextension and/or rotation stresses the pars interarticularis and can cause injury if not appropriately managed.
Therefore this injury is commonly seen in young athletes who participate in ballet, gymnastics, and cricket (particularly fast bowlers).
The Spectrum of a Pars Injury
An injury to the pars interarticularis can range from a stress response to the small segment of bone (seen on imagining as bony bruising or oedema) which can later progress to a stress fracture (also known as a spondylolysis) if the pars has not had a chance to heal. If a fracture occurs, this means the lower and upper facet joints of the vertebral spine can become separated. This can happen on one or both sides of the spine.
A pars fracture can increase the risk of developing other conditions such as:
- Spondylolisthesis (vertebral slippage)
- Nerve root irritation or compression
- E.g. Sciatica, referring leg pain and/or weakness
- Chronic pain
Is a Pars Injury a Serious Condition?
A pars injury should be taken seriously due to the risk of developing other conditions that can impact a person’s quality of life and participation in sport, if left untreated. Treatment depends on the degree that the pars is injured (i.e. bone stress vs complete fracture, or one side vs both sides).
A thorough history and assessment completed by your healthcare professional is vital, as this will determine whether further imaging is warranted to determine the cause of any back pain.
A pars injury is confirmed with an MRI scan as this is the most sensitive scan to identify a pars injury.
An MRI scan can identify a pars injury, however further investigation with a CT scan may be necessary to determine whether the bone is still intact.
X-rays of the lumbar spine are not as sensitive as an MRI in detecting a pars injury as they cannot identify any bony stress. However, an x-ray may be able to detect a chronic pars fracture due to the bone separation (“scottie dog with a collar sign”) and a spondylolisthesis (vertebral slippage).
Prognosis of a pars injury will be determined by the severity of the injury.
If the pars injury is detected prior to becoming a stress fracture, and with appropriate management, the patient can expect to make a full recovery usually within a 3-6 month period.
If the pars injury has developed into a fracture on one side, the recovery and return to sport time frame is longer however a return to sport is to be expected. This can take anywhere from 6-18 months or longer.
If the pars injury is on both sides of the spine and/or the patient is experiencing a lot of pain or neurological symptoms a specialist opinion is required to determine whether surgical intervention is necessary and if the patient can safely return to their desired sport.
All pars injuries related to sport require a Sports Medicine Specialist opinion to determine the severity of the injury and outline all contributing factors such as high risks activities, diet and general health. Other healthcare professionals that are involved with management include a general practitioner, physiotherapist and at times a dietician, orthopaedic specialist and/or paediatrician.
Generally, if the pars shows signs of bone stress a period of rest, exercise rehabilitation will allow the pars to heal. This is then followed by a gradual return to sport.
Exercise rehabilitation usually involves core strengthening, hamstring stretching and activity modification to avoid additional extension forces on the pars. Strengthening exercises initially focus on static core exercises with a slow progression to flexion then extension based exercises once, ensuring that the exercises are not aggravating any pain. This is done under the guidance of a physiotherapist.
If the pars injury has developed into a complete fracture and is one sided, a period of rest and exercise rehabilitation is usually first line treatment. The fracture will not heal, however with rehabilitation, a gradual return to sport can be expected if there a no other complications caused from the pars fracture (e.g. spondylolisthesis and or neurological symptoms).
If the pars fracture is on both sides, or if there is a spondylolisthesis or neurological symptoms the patient may need to have surgery to stabilise the joint or address the structure causing the neurological symptoms.
If surgery is necessary, rehabilitation is encouraged to help the patient return to a functional baseline, however it will be determined by the specialist whether the patient is safe to return to their desired sport. They will also be able to advise the patient about other sports/activities they can safely participate in to avoid re-injury.
- Pereira Duarte M, Camino Willhuber GO. Pars Interarticularis Injury. [Updated 2023 Feb 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK545191/
- Ranawat V (2018) Stress fractures of the lumbar spine in cricketers: A suggested rehabilitation programme post surgery. https://www.oatext.com/stress-fractures-of-the-lumbar-spine-in-cricketers-a-suggested-rehabilitation-programme-post-surgery.php
- Kiel J, Kaiser K. Stress Reaction and Fractures. [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507835/
- Linton AA, Hsu WK. A Review of Treatment for Acute and Chronic Pars Fractures in the Lumbar Spine. Curr Rev Musculoskelet Med. 2022 Aug;15(4):259-271. doi: 10.1007/s12178-022-09760-9. Epub 2022 May 2. PMID: 35499747; PMCID: PMC9276862. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9276862/
- Mansfield JT, Wroten M. Pars Interarticularis Defect. [Updated 2023 Jun 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538292/
- Selhorst M, Allen M, McHugh R, MacDonald J. REHABILITATION CONSIDERATIONS FOR SPONDYLOLYSIS IN THE YOUTH ATHLETE. Int J Sports Phys Ther. 2020 Apr;15(2):287-300. PMID: 32269862; PMCID: PMC7134351.