61) Yuan HA, Garfin SR, Dickman CA, Mardjetko SM. A historical cohort study of pedicle screw fixation in thoracic, lumbar, and sacral spinal fusions. Spine 1994;20S:2279S-2296S.
6) St. John TA, Alber TJ. "Reduction of Spondylolisthesis with Pedicle Screw Fixation And Transforaminal Lumbar Interbody Fusion." In Surgical Techniques for the Spine; Haher TR, Merola AA; Thieme – New York 2003.
62) Gehrchen PM, Dahl B, Katonis P, et al. No difference in clinical outcomes after posterolateral lumbar fusion between patients with isthmic spondylolisthesis and those with degenerative disc disease using pedicle screw instrumentation. Eur Spine J 2002; 11:423-427.
80) Liu XY, et al. Meta-Analysis of Circumferential fusion versus Posteriolateral Fusion in Lumbar Spondylolisthesis. J Spinal Disord Tech 2014; 27:E282-293.
In a landmark and somewhat controversial study, Herkowitz et al.  prospectively studied the surgical outcomes of two groups of patients with lumbar degenerative spondylolisthesis with associated stenosis. Specifically, one group (n=25) was treated with laminectomy, and the other group (n=25) was treated with laminectomy plus non-instrumented posterolateral fusion (PLF). Both groups were carefully followed after surgery for a minimum of two years in order to see how they were doing. At the final follow-up, which averaged three years from the date of surgery, the patient's who had undergone fusion plus decompression demonstrated statistically superior clinical outcomes, as compared to the group that had only had decompression. The authors concluded by saying:
Because there is no fracture to deal with in degenerative spondylolisthesis, many surgeons once believed that no lumbar fusion was indicated. Instead, a simpler decompression (aka, laminectomy, laminotomy, foraminotomy) was the way to go.
There was, however, one lower quality systematic review  that pooled the data from nine of the highest quality (only level III and IV evidence) direct repair papers (a mixture of Scott's wiring technique and Buck's procedure) and compared them with fusion (mainly PLF). After analyzing data from the two groups, Westacott et al. concluded that there was no statistical difference between direct repair and fusion with regard to clinical outcomes.  What do these results mean? Well, if true, they mean the patient can choose the Buck's procedure over fusion, which in turn will ostensibly preserve the lumbar spine biomechanics and eliminate the chance of suffering the post-fusion domino effect.
Since the goal of fusion for spondylolysis is to stabilize the fractured posterior arch, typically a less invasive type of fusion is employed, such as posterolateral (PLF) fusion with instrumentation. Although instrumented PLF does not invade the epidural space (which is a very good thing), like the other types of fusion, it does destroy the normal biomechanics of the lumbar spine, which in turn overloads the adjacent vertebrae. Such an overload will make them vulnerable to new injury, chronic pain, and possibly the need for subsequent fusion—a phenomenon often referred to as "the domino effect."
Again, Thirukumaran et al demonstrated that the posterior procedures (transforaminal lumbar interbody fusion and posterior lateral interbody fusion) are becoming far more popular than anterior lumbar interbody fusion and/or 360° fusion (PLIF + PLF). How much more popular? Since 1998, there has been a 330% increase in the use of the posterior procedures; the anterior procedure has really fallen out a favor.
In 2009, Weinstein et al. published the results of their investigation (which was part of the famous SPORT studies) that answered the question, "Does spine surgery outperform non-operative care?"  In order to answer the question, they followed over 300 patients, approximately half had conservative care and the other half underwent lumbar fusion, for four years and then reevaluated them. After reviewing all the data, they concluded that the patients who had undergone lumbar fusion demonstrated superior clinical outcomes with regard to the ability to function and pain levels, as compared to the patients who had only used non-operative care.