A Prognostic Evaluation of Back Pain Resolution Following Total Disc Replacement View PDF

Spinal fusion has traditionally served as the primary surgical intervention for CLBP. Nevertheless, fusing a spinal segment can adversely affect the physiological and biomechanical function of adjacent segments and the spinal column as a whole [1]. The loss of motion at a fused level may redistribute stress to neighboring segments, potentially accelerating degenerative changes — a phenomenon termed ASD [2, 3]. A systematic review of kinematic investigations demonstrated that while most patients exhibited no generalized kinematic alterations at segments cranial or caudal to the fusion site, a subset (approximately 20 - 30%) developed pronounced kinematic instability at the cranial adjacent level following lumbar fusion [4]. These observations prompted the development of non-fusion, motionsparing surgical techniques. TDR was introduced to mitigate the complications associated with ASD by maintaining mobility at the operated level. Symptom relief following TDR is believed to result from both the removal of the pathological disc and the restoration or enhancement of load transmission across the segment [5, 6]. A cochrane review concluded that TDR appears effective for managing low back pain in appropriately selected patients and yields outcomes at least comparable to fusion in the short term [7]. The observed differences in clinical improvement fell within generally accepted thresholds for clinical equivalence. Findings from a randomized controlled trial (RCT) directly comparing fusion and TDR favored TDR over fusion at both the 2- and 5-year follow-up intervals [8, 9]. Notably, a greater proportion of patients in the TDR cohort reported complete absence of pain. In general, lumbar range of motion (ROM) tends to diminish following spinal fusion.

Research has shown that preserving or restoring segmental mobility helps avert abnormal stress and altered kinematics at adjacent levels [10]. Multiple investigations have characterized post-TDR kinematics and load distribution, with reports demonstrating near-normalized or fully normalized motion patterns [11, 12]. Conversely, one study found no association between clinical outcomes and the extent of segmental mobility following TDR [13]. In a long-term follow-up of patients implanted with an early-generation Charité prosthesis, 60% underwent spontaneous fusion over a 17-year period; paradoxically, these patients experienced superior clinical results compared with those whose segments remained mobile [14]. No radiographic evidence of ASD was detected among patients who retained mobility. Additional studies have documented even more favorable outcomes with this early prosthesis design [15, 16]. The literature remains divided regarding facet joint loading: some reports describe unchanged facet loads, while others provide evidence of increased facet joint forces following TDR [11, 12, 17].

A comparative analysis of segmental mobility derived from the aforementioned RCT, based on 2-year postoperative assessments, has been previously reported [18]. Because postoperative kinematic changes at both operated and adjacent segments are likely to evolve over time, investigations with extended follow-up periods are needed [7].