Spondylolysis, defined as a defect of the vertebral pars interarticularis, is estimated to occur in 3% to 7% of adults and is usually clinically asymptomatic (1,2). For patients with symptomatic spondylolysis, a variety of management strategies have been advocated (3,4,5). Conservative management resolves the problem of pain in most patients and should be attempted prior to surgery. The alternative forms ofnonsurgical treatment may include rest, adaptation of physical activity and sports, active physiotherapy, bracing, and medication. Activity restriction followed by rehabilitation and strengthening exercises are often successful in improving symptoms (3). Nonetheless, a small percentage of patients fail conservative treatment, and a surgical alternative may be considered for this subgroup (6).

Several procedures have been proposed and used over the years for the surgical management of symptomatic spondylolysis or spondylolisthesis with minimal displacement. The traditional surgical procedure to manage this condition has been spinal fusion (6); decompression by total excision of the loose lamina (7) with or without fusion has also been advocated. As an alternative to fusion techniques that eliminate a mobile segment, surgical procedures repairing only the pars defect were introduced (4,8). The aim of this surgery is to ensure consolidation of the pars interarticularis fracture without modifying the functional anatomy around the defect. With the restoration of normal anatomy, preservation of motion at the affected spinal segment is theoretically possible. Surgical success is directly related to accurate localization of the source of pain. In a patient with a pars defect, pain can potentially originate from the defect itself or from an adjacent degenerative disc (9). Most reports point out that the ideal candidates for direct repair are younger patients without degenerative findings, but identification of the actual source of pain may be more important than the consideration of age (10). Several diagnostic tools have been used to select ideal surgical candidates: Pars infiltration to confirm the pars defect as the source of pain, and magnetic resonance imaging (MRI) and discography to rule out discogenic pain.

In 1968, Kimura (8) was the first to introduce direct repair of the defect, using bone graft without any internal fixation. Patients were confined to bed-rest for 2 months and thereafter wore a brace for an additional 4 to 6 months. In 1970, Buck was the first to use internal fixation (lag screws) across the pars interarticularis to repair the fracture (4). Other authors have since reported direct repair of the pars defect using wire (11,12,13,14), hook screws (15,16,17,18,19,20), cable-screws (21), screw-rod hooks (22,23,24,25), and other internal fixation techniques (26,27).

Buck admitted that accurate placement of translaminar screws is technically difficult (28). The technique requires considerable skill, and with relatively few cases being operated, most
surgeons will have limited surgical experience (14). Scott was the first to apply a simple and effective means of repairing spondylolytic defects through the use of bone grafts and wiring in 1968. However, his results were not published until 1986 (14). It was later found that segmental wiring can also be accompanied by technical difficulties when passing the wire under the transverse process of L5, because of the overlapping iliac crest (12). Furthermore, placement of the wire under the transverse process can lead to substantial bleeding and carries a risk of nerve root injury (20).

In order to avoid passing a wire around the transverse process, the use of pedicular screws to anchor the tension band wire was suggested in 1993 (27). In this modified screw-wire technique, the wire is anchored around the spinous process to hold down graft bone that bridges the pars defect. However, with this system, the compression force exerted against the graft bones is diverted away from the lamina. The strength and linkage of wires as well as the inadequate direction of the force attained through fixation are unfavorable for achieving fusion (25). The use of Buck screws across the pars defect is advantageous in that the direction of the compression force they exert is the same as that of the lamina. Nevertheless, the presence of the screw limits the size of the bone graft mass on the surface of the defect.

In 1984, Morscher introduced the screw-hook technique (29). As compared with the compression screw alone, the hook had the advantage of providing a solid grasp in dysplastic vertebral arches. The main problem with the Morscher technique was seen to be the high incidence of screw loosening, which presented as swelling and pain (18,20).

Pseudoarthrosis may develop after repair of the defect and often leads to poor clinical results (13,19,30). The most frequent cause of pseudoarthrosis has been found to be the use of internal fixation techniques that do not provide sufficient stability (31). More rigid fixation techniques lead to a lower prevalence of pseudoarthrosis and hence, better clinical results. The clawlike configuration of the screw-rod-hook construct, which incorporates elements of standard spine instrumentation, offers good mechanical stability (32). However, a potential drawback of this technique lies in the bulkiness of the instrumentation, which makes radiographic evaluation of the pars difficult (24). Although several studies have analyzed the effectiveness of the different systems, the series are small in number and no comprehensive or detailed comparisons among them have been made. These reduced bibliographic reviews do not appear to favor any one surgical technique over another (18).

Professional athletes have a higher prevalence of isthmic defects than the general population (33). It is currently believed that the most likely cause of isthmic spondylolysis in athletes is a fatigue fracture. A direct relationship has been observed between this condition and intense sports activities in athletes between the ages of 5 and 15 years (34). Most patients with symptomatic spondylolysis in general, and professional athletes in particular, have mechanical back pain related to activity and movement. This is a limitation that prevents such athletes from performing at a maximum level. If symptoms are not reduced through conservative measures, the affected athlete must either retire from sports activities or undergo some type of surgical treatment. When surgery is chosen, however, a relatively long period of activity restriction is required, which usually leads to deterioration in athletic performance. The implications of these factors cause both physicians and athletes to hesitate before considering surgery. At present, information is insufficient concerning the long-term outcome of athletes treated for symptomatic spondylolysis in terms of their return to sports activity (34).