Open Discectomy with and Without Interpositional Grafting
If the patient has failed all arthroscopic measures and falls into a category Wilkes IV or V, the next surgical step is typically discectomy. The discs are usually dysmorphic and are irreparable. Discectomy involves removing the entire avascular portion of the disc and inflamed retrodiscal tissue. Despite the open surgical approach, it can be very challenging to access all aspects of the disc, especially the medial aspect. The most controversial aspect of performing discectomy is the need for reconstruction and what material to use. The anatomical goal following discectomy is the formation of a pseudo-disc composed of dense collagen. This in theory would serve to provide some load distribution and reduce degenerative changes within the condyle and eminence. This has been routinely observed following discectomy. The purpose of using an interpositional graft is to facilitate the development of the pseudo-disc by placing tissue between the condyle and fossa at the time of surgery.
Patient-reported outcomes after discectomy without replacement have also been reported to be successful in more than a 90% of patients as assessed with pain, MIO, and function [39-47]. Postoperative changes following discectomy typically include progressive degenerative joint disease [39, 42, 48-50]. It remains unclear whether these changes are more severe than those following the use of an interpositional graft. Furthermore, the clinical significance of these changes may be unimportant given the long-term data supporting pain reduction and increase in the MIO and function.
Fig. 11.17 Condylar changes 1 year after discectomy with temporalis flap to left temporomandibular joint. (a) Coronal view. (b) Sagittal View. (c) 3D view
Progression of condylar changes and resorption after discectomy can potentially be delayed or reduced by the placement of an interpositional graft. Interpositional grafting materials include fat, auricular cartilage, full thickness skin, fascia and dermis, temporalis muscle, allogeneic grafts, and temporary Silastic. Each material has its advantages and disadvantages with little scientific evidence to support or refute the material chosen. All have been shown to reduce pain and improve function in a majority of appropriately selected patients. All can be expected to result in radiographic condylar changes consistent with progressive degeneration despite improvement in pain and function (Fig. 11.17a-c).
The potential for iatrogenic degenerative joint disease appears to be greatest following open joint procedures. Although counterintuitive, the development of degenerative joint disease following many varying open joint procedures does not appear to correlate with patient outcomes despite clear radiographic evidence in many patients. This suggests that the inflammatory milieu and disc position/shape and their respective treatment are more important than radiographic features of DJD in predicting patient outcomes. However, the development or progression of degenerative joint disease following discopexy or discectomy with or without replacement does influence the nature of the subsequent surgery should it become necessary.