The effect of fat grafts or gelatin sponges, which are used by some surgeons to cover the laminectomy site prior to closure, is unknown. It is unclear whether or not the presence of a fat graft could prevent early recurrent extruded disc material from spontaneously moving away from the spinal cord, thus increasing the risk of postoperative clinical deterioration [5] (see Chapter 34). The effect of early postoperative rehabilitation on recurrent disc herniation is also unknown. Several recent publications describing early recurrence of disc extrusion at the site of surgery included dogs that received underwater treadmill therapy within 2–3 days of surgery and were reported to develop early signs of recurrent disc extrusion confirmed with imaging and/or surgery [3, 7, 9].

The overall conclusion is that decompression alone does not prevent any remaining nucleus pulposus from extruding through the damaged AF in the postoperative period and that fenestration of the affected disc space should be performed when possible to reduce the risk of early recurrent herniation [3, 5, 10]. Although early recurrence has been reported to occur in spite of disc fenestration [5], other studies have shown that fenestration of the affected disc space prevented early recurrence in all reported cases [3, 10].

Early recurrence

Early recurrence reportedly occurs within 4–6 weeks of surgery and is most commonly associated with recurrent nuclear extrusion at the site of initial IVD extrusion [3, 11, 12]. Differential diagnoses for early postoperative deterioration or failure to improve postoperatively include iatrogenic trauma, failure to remove the compressive mass at surgery, continued or second disc herniation, hemorrhage, infection, spinal instability, and myelomalacia [5, 7–9, 13]. Although the potential for early recurrence should be considered in patients showing deterioration after initial postoperative improvement, an early recurrence rate of only 2% over a 4-year period was reported in a recent study [7], which is consistent with the rate of 1% over 15 years previously reported in another study [11]. Lack of improvement after decompressive surgery has generally been associated with the disease process itself (primary and secondary spinal cord injury) or with the presence of residual disc material within the vertebral canal. The presence of residual disc material after surgery is thought to be influenced by the surgeon’s ability to evacuate disc material [9, 11]. In a study that reviewed 178 postoperative cases of TL IVD herniation, 10 dogs (5.8%) had clinical deterioration within 1–10 days of surgery, some for residual disc at the site of initial surgery and others because the initial surgery was performed at a site immediately adjacent to the affected disc space resulting in only partial removal of the extruded disc material [9]. Of the 10 dogs in the study, 8 underwent a second surgery to remove residual disc material and recovered uneventfully. In contrast, a recent study found residual disc material in 100% of 40 dogs when assessed by computed tomography (CT) immediately following hemilaminectomy [8]. In contrast to the previously mentioned studies, residual disc material was not surgeon dependent in this study and was not associated with failure to achieve a functional recovery [8]. Similarly, a study evaluating residual disc material by comparing pre- and postoperative MRI found residual material in 10 of 10 dogs following hemilaminectomy and 4 of 9 dogs following mini-hemilaminectomy for an extruded TL disc [14]. This suggests that the presence of residual material is possible with various surgical techniques [14]. Since clinical recovery is the most important postoperative factor, repeat diagnostic imaging should be performed when feasible in any patient that fails to improve or deteriorates postoperatively [7, 9, 11].

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