Spondylolysis is a common cause of low back pain in adolescents particularly those that participate in athletics which involve hyperextension of the lumbar spine. The prevalence of pars defects in the general population has recently been shown to be as high as 11% with the use of CT imaging as a more sensitive mode of detection instead of the previously accepted 6% which was assessed with plain radiographs. (5)
Pars defects associated with low back pain have been reported as high as 80% in adolescent athletes. (9) The current treatment guidelines for spondylolysis are bracing and immobilization for an average of 3 to 6 months, with a gradual return to strength training and competition after that. (2) While a nonunion may remain asymptomatic in the first five decades of life, a correlation between slip progression and disc degeneration has been shown. (3) The micromotion that is allowed to take place with bracing treatment not only delays healing of the defect but creates a hypermobile vertebral segment, thus accelerating disc degeneration.
Fibrocartilaginous hypertrophy at the site of the defect causing radicular symptoms has also been described in the literature. (4) It is reasonable to assert that if the pars defects were to be surgically reduced and fixated allowing for primary bone healing, there would be an accompanied decrease in intervertebral disc disease seen in this population. Pseudo-bilateral defects have also been described as bilateral defects with asymmetric uptake on SPECT which have been shown to have no chance of healing. (10)
The current literature poorly describes anatomical healing results from non-operative treatment and prefers to use clinical outcomes as measurement. As life expectancy increases and more patients live through the fifth decade of life, the incidence of patients becoming symptomatic from the natural progression of the disease continues to rise. Patients that are relatively healthy and desire to continue to lead an active lifestyle may require a fusion, however the natural history of the disease progression could be avoided through early surgical intervention. Early intervention carries the added benefits of younger patients that have a greater ability to recover from an operation in addition to the mitigation of chronic degeneration of the discs. The second option being later in life when patients have a less robust ability to recover from surgery and have suffered the chronic sequelae from the pars defect such as spondylolisthesis, slip progression, chronic back pain, or radiculopathies.
As a principle of orthopedics, solid osseous union in fractures is the preferred outcome, whereas nonunion is not commonly acceptable. Traditional spine surgery carries with it a very cumbersome recovery period due to the large incision and highly invasive technique causing trauma to the soft tissues in the approach to the spine, along with a psychosocial toll that made nonoperative treatment a more appealing option. The evolution of minimally invasive spine surgery, image guidance techniques, and the use of biologics have greatly improved recovery time for this procedure and make surgical intervention a much more favorable treatment option.
Pre-Operative Plan and Imaging
An 18 year old male presents to the office with sharp, right sided low back pain that began 2 months prior from a flag football injury. The patient had tried over the counter anti-inflammatory medications and home exercise programs without relief. Radiographs were obtained upon presentation to the office which demonstrated some loss of disc space height at L5-S1 and an acute right sided spondylitic pars fracture with no evidence of a left sided pars defect (Figure 1.A, 1.B).
Fig. 1.A Lateral Radiograph
Fig. 1.B RPO Radiograph
An MRI was ordered to advance his workup which demonstrated a poorly visualized right L5 pars and an intact left L5 pars (Figures 2.A, 2.B, 2C). A brace and non-operative treatment was recommended at this time as well as obtaining a SPECT to evaluate for an acute or metabolically active pars defect.
Fig. 2.A L5 Axial T2 MRI
Fig.2.B Sagital STIR MRI
Fig.2.C Sagital T2 MRI
The SPECT demonstrated a right sided L5 pars defect with increased uptake confirming a right L5 spondylolysis (Figures 3.A, 3.B, 3.C, 3.D).
Fig.3.A SPECT 3D Reconstruction
Fig.3.B Sagital SPECT
Fig.3.C Axial CT of L5
Fig.3.D Axial SPECT L5
At this time the patient was provided an LSO brace to wear for the next six weeks to allow for healing of the acute sponylitic pars fracture. The patient was allowed to begin to wean out of the brace and initiate a course of physical therapy. The patient retuned to the office three months later complaining of pain in the afternoon after attempting to return to early sports participation and does not feel as though he can resume full activity at this time. Radiographs were obtained and demonstrated a persistent right L5 pars defect with no defect in the left L5 pars (Figure 4). The patient has been symptomatic for 8 months without relief from non- operative treatment options. The patient decided to proceed with operative fixation at this point for definitive treatment. At one month post-op the patients incision was healed (Figure 5) and the patient is now seven months out from surgery with no complaints or physical limitations (Figure 6).
Fig.4 RPO Radiograph
Fig.5 1 month postop
Fig.6 7 month postop
Intraoperative fluoroscopy was used to localize the level of incision and a midline incision was drawn out over the tip of the spinous process of the affected vertebral segment. A one inch right sided paramedian incision was made in the fascia and a muscle sparing approach was made down to the level of the pars using intraoperative fluoroscopy. Retractor was placed and docked over the pars and after the muscle and soft tissue were dilated, the pars defect was identified. A combination of curette and 3 mm high-speed matchstick bur was then used to remove the fibrous tissue interposed in the fracture site. The edges of the pars cephalad and caudally were decorticated down to punctate bleeding bone to allow for healing potential (Figure 7).
Fig. 7 Removal of fibrous tissue and decortication with curette
Intraoperative fluoroscopy was again used to confirm and identify the pars fracture. The intraoperative microscope was used throughout for microsurgical evaluation and decortication and removal of the fibrous nonunion. The area was copiously irrigated and bone graft, including local autograft and some allograft bone, was then packed into the pars defect. An O arm spin was performed. The targeting guide was placed on the caudal aspect of the spinous process of the vertebral segment above the fractured prior to the spin. A separate more caudal incision was made to allow for adequate trajectory in line with the pars. Sequential dilating was performed down to the starting point in the lateral aspect of the lamina just adjacent to the inferior auricular process. A pilot hole was drilled and then a guide-pin was placed using a combination of direct visualization of the pars as well as Stealth navigation. The guidewire was drilled and placed across the pars defect and positioned in the pedicle at the junction of the transverse process. The screw was measured to be 35 mm in length and a 3.0 drill bit was used to drill over the guidewire and a 4.5 partially-threaded lag screw was placed using lag by design method across the pars defect. Excellent fixation and compression was achieved with the screw and a washer. A final O arm spin was performed which confirmed appropriate position of the hardware, and the fracture to be well reduced (Figure 8.A, 8.B, 8.C).
Fig. 8.A Axial O arm CT
Fig. 8.B Sagital O arm CT
Fig. 8.C Oblique O arm 3D recon
Accepting a pseudarthrosis defies orthopedic principles of fracture care. Unilateral defects may heal but Beutler et al reported only three of eight patients healed. Bilateral defects are much more common, do not heal, are at a very high risk for spondylolisthesis and have greater risk of slip progression in the earlier decades of life. There were two groups that were identified with bilateral defects, those that were diagnosed by 7 years of age and those that were diagnosed between the ages of 12 to 25 years of age. There were 16 patients that were identified by seven years of age, 10 of which had already suffered some degree of spondylolisthesis with an average of 11%.
There were six patients that were identified between 12 to 25 years of age, 5 of which experienced slippage of 10-30%. Not a single patient achieved complete resolution of the defect by solid osseous union. (1) This may be explained through the mechanism of secondary bone healing via bracing which leads to a less rigid immobilization of the fracture. (6) Of the 22 patients with bilateral defects, 18 of them developed spondylolisthesis. The average rate of slip progression was 7% in the first decade of life and decreased to 4% in the second and third decades of life. The timing of segmental laxity also played a role as early laxity saw 7-20% increase in the slip whereas late laxity saw a 0-14% increase. (1) Bilateral defects are subject to further fragmentation and spurring of the pars over time, as well as degeneration of the intervertebral discs from the lack of stability. (7)
We propose that solid osseous union is possible through the use of less invasive surgical techniques in conjunction with image guidance abilities. This should lead to a quicker recovery and prevent further sequelae of these injuries such as spondylolisthesis, slip progression, chronic back pain, radiculopathies and the need for future procedures including pain management or ultimately lumbar fusion. A meta-analysis reviewed several techniques for direct pars repair including the Buck method, first described in 1970, which is most similar to the technique described in our paper. The direct fixation using a lag screw across the defect had up to a 100% fusion rate and optimal screw placement being the main technical difficulty. (8) With the assistance of advanced image guidance as used in our case, we were able to confirm an optimal approach and placement of the screw.
In our paper, we describe a less invasive technique for pars fracture repair and present a case as an example of the increased morbidity associated with failure of non-operative treatment in comparison to surgical intervention with our technique. The patient is now seven months out from surgery and is without setbacks or limitations. Through surgical correction we can manage this patient with a more definitive solution and predictable outcome. Patients will regain their quality of life sooner and the potential long term sequelae will be mitigated.
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- Mohammed, N., Patra, D. P., Narayan, V., Savardekar, R., Dossani, R. H., Bollam, P., Nanda, A. (2018). A comparison of the techniques of direct pars interarticularis repairs for spondylolysis and low-grade spondylolisthesis: a meta-analysis. Neurosurg Focus, 44(1), E10. doi:10.3171/2017.11.FOCUS17581
- Panteliadis, P., Nagra, N. S., Edwards, L., Behrbalk, E., & Boszczyk, B. (2016). Athletic Population with Spondylolysis: Review of Outcomes following Surgical Repair or Conservative Management. Global Spine Journal, 6(6), 615-625. doi:doi:10.1055/s-0036-1586743
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