The major finding of our study is that the vast majority of patients who had undergone TMJ discectomy were satisfied with the long-term results and that their symptoms had improved after surgery. From a long-term perspective, discectomy thus can significantly improve jaw function, leading to reduced TMJ pain, locking, and clicking. This outcome corresponds with outcomes in the 6-month follow-up in this patient cohort [21]. We did not distinguish crepitation from clicking in our long-term follow-up, but there was a significant postoperative reduction in TMJ sounds. Previous studies have shown a significant reduction in clicking but not crepitation, which is mentioned as a commonly occurring symptom in other studies. Crepitation has no clear correlation with pain but is believed to be part of the remodeling process of the joint [13, 20, 28]. Headaches also decreased significantly among our patients after discectomy. One interesting observation is the long pre-operative conservative treatment period prior to the discectomy. In the current treatment regime in our team, the patient is evaluated after 6 months of conservative, for decision of eventually surgical interventions. The length of time for the pre-operative treatment may thus affect the outcome of the surgical treatment.

In the 6-month analysis of this cohort [21], mouth opening had improved significantly from a mean 36.7 mm to 41.8 mm. Half of the patients who had a jaw opening capacity of 41–60 mm before surgery had a reduced jaw opening range after surgery. This status at 6 months may underlie our current results indicating that limited opening did not improve significantly after discectomy (p = 0.083). These findings deviate to some extent, however, from other long-term studies that have described a jaw-opening capacity > 39 mm in most patients after surgery [22,23,24].

The success of discectomy depends on which parameters are chosen as outcome criteria. In our earlier retrospective 6-month follow-up study, the findings were based on patient record data from clinical examinations and followed a modified version of the American Association of Oral and Maxillofacial Surgeons criteria [21]. Our questionnaire focused on each patient’s subjective view of TMJ symptoms, and symptoms such as crepitation could have been registered differently. Most of the patients had undergone the procedure many years ago, and the precision of their memory of the experience likely varies. Recall of level of satisfaction may be accurate, but memory of specific symptoms before or after the operation may be less stable. Differences in outcomes have been noted in other studies of success rates for other treatments, with large discrepancies between the patient assessments (78%) and clinical criteria (7%) [29].

In our cohort, based on the patients’ subjective experiences after discectomy, the outcome can be viewed as satisfactory overall. Still, a considerable proportion of patients had to seek further care for persistent symptoms, most commonly pain with chewing and jaw opening. A qualitative study with interviews likely would yield further insight into their perspectives. In other long-term studies, no pain or only occasional pain was reported, with pain from the non-operated joint being more common, warranting treatment with analgesics [22, 24]. We found that pain from the operated joint was more common. Studies may differ in these outcomes because of variations in how pain was assessed, such as not presenting tenderness or stiffness as pain, which our patients may have done in responding to our questionnaire [22,23,24].

The patients in our study who had to seek care postoperatively had higher CPI scores for general pain at 24–33 postoperative years. These experiences may reflect other comorbidity factors such as pain in the spinal region, fibromyalgia, or depression [30,31,32]. It also is possible that there was some uncertainty about whether the question referred to general pain in the body or in the face region only. One register-based study showed that patients with more than one TMJ surgery had more psychiatric diagnoses and were on sick leave significantly more often than controls, indicating a more complex psychosocial comorbidity [33].

Satisfaction did not differ statistically between patients who had to seek care again and those who did not (p < 0.144). A possible implication is that even patients with remaining symptoms after the discectomy were still satisfied with the overall result. For the thirteen patients, which did not need re-operation, the number of further treatment decreased indicating a reduced treatment need.

Our questionnaire asked patients only to answer “yes” or “no” without any further comment or query about whether symptoms had increased or decreased postoperatively or if they were constant or occasional, as other studies have done [22,23,24].

Six patients (13%) had been reoperated, and they reported higher dissatisfaction with the surgical result. Approximately the same frequency of reoperations and postoperative treatments have been reported in the literature [20, 22,23,24, 34].

A crucial factor in these outcomes related to reoperation is postoperative rehabilitation. Rehabilitation is essential to avoid fibrous ankylosis, especially when bleeding in the joint space has occurred. Other factors also may be in play. A case–control study with prospectively collected data from Swedish national registries, analyzed the presence of mental and behavioral disorders and the probability of developing TMD. Their findings indicated an increased probability of TMD among patients with a history of certain mental and behavioral diagnoses, and a stronger association with TMD requiring surgery, specifically repeated surgery. This finding highlights the need for improved preoperative understanding of the impact of mental and behavioral conditions on TMD, as TMD and chronic pain can negatively affect mental health. Overall, it is obvious that reoperations do occur, and patients must always be informed about these risks before a discectomy [33].

One limitation of this study was the small number of reoperated patients (n = 6), which precludes drawing firm conclusions for this group. Of the overall patient cohort, 83% were women. Women tend to report severe pain more frequently than men do, which may have been a factor in our results [1, 8], although several other studies have had a similar gender distribution [16, 28, 34]. Life events that could affect discectomy outcomes also can influence long-term follow-up, including psychological factors, medication, overall pain, and comorbidity. This study lacked a control group and also does not support comparisons between discectomy and outcomes with other treatments. The authors of a systematic review comparing various surgical options concluded that despite better outcomes on some measures after discectomy, invasive surgical procedures should not be implemented as a first-line option for arthrogenous TMD management [35].