The lexicon for periprosthetic bone loss versus osteolysis after cervical disc arthroplasty: a systematic review

Abstract

Background Periprosthetic bone loss is a common observation following arthroplasty. Recognizing and understanding the nature of bone loss is vital as it determines the subsequent performance of the device and the overall outcome. Despite its significance, the term “bone loss” is often misused to describe inflammatory osteolysis, a complication with vastly different clinical outcomes and treatment plans. Therefore, the goal of this review was to report major findings related to vertebral radiographic bone changes around cervical disc replacements, mitigate discrepancies in clinical reports by introducing uniform terminology to the field, and establish a precedence that can be used to identify the important nuances between these distinct complications. Methods A systematic review of the literature was conducted following PRISMA guidelines, using the keywords “cervical,” “disc replacement,” “osteolysis,” “bone loss,” “radiograph,” and “complications.” A total of 23 articles met the inclusion criteria with the majority being retrospective or case reports. Results Fourteen studies reported periprosthetic osteolysis in a total of 46 patients with onset ranging from 15–96 months after the index procedure. Reported causes included: metal hypersensitivity, infection, mechanical failure, and wear debris. Osteolysis was generally progressive and led to reoperation. Nine articles reported non-inflammatory bone loss in 527 patients (52.5%), typically within 3–6 months following implantation. The reported causes included: micromotion, stress shielding, and interrupted blood supply. With one exception, bone loss was reported to be non-progressive and had no effect on clinical outcome measures. Conclusions Non-progressive, early onset bone loss is a common finding after CDA and typically does not affect the reported short-term pain scores or lead to early revision. By contrast, osteolysis was less common, presenting more than a year post-operative and often accompanied by additional complications, leading to revision surgery. A greater understanding of the clinical significance is limited by the lack of long-term studies, inconsistent terminology, and infrequent use of histology and explant analyses. Uniform reporting and adoption of consistent terminology can mitigate some of these limitations. Executing these actionable items is critical to assess device performance and the risk of revision. Level of Evidence IV Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Observations of bony ongrowth and clinical fixation in two retrieved disc replacements

“…Therefore, the cause of the observed osteolysis could not be determined. Regardless, the etiology of osteolysis is rarely studied in spinal implants and, specifically, the multifactorial relationship between osteolysis and successful fixation remains unclear, requiring further exploration 20 . Furthermore, the age of the patients included in this study was quite different (66 years vs. 36 years), which may have influenced the potential for bony ongrowth.…”

“…[15][16][17] Further, case reports have identified infection and osteolysis as rare complications in M6-C devices. [18][19][20][21] Unfortunately, M6-L clinical studies and case reports are relatively rare, with the majority of studies assessing short-term outcomes and reporting overall reduction in pain and restoration of motion. 22,23 Furthermore, the presence of bony ongrowth and overall fixation of these devices have not been assessed for the M6 cervical or lumbar devices.…”

“…Previous clinical studies identify adjacent segment degeneration (ASD) and heterotopic ossification (HO) as commonly observed complications 15–17 . Further, case reports have identified infection and osteolysis as rare complications in M6‐C devices 18–21 . Unfortunately, M6‐L clinical studies and case reports are relatively rare, with the majority of studies assessing short‐term outcomes and reporting overall reduction in pain and restoration of motion 22,23 .…”

“…Regardless, the etiology of osteolysis is rarely studied in spinal implants and, specifically, the multifactorial relationship between osteolysis and successful fixation remains unclear, requiring further exploration. 20 Furthermore, the age of the patients included in this study was quite different (66 years vs. 36 years), which may have influenced the potential for bony ongrowth. However, conflicting literature suggests that age may not be a factor in bone ongrowth for joint replacements.…”

Proposal for a classification system of radiographic bone changes after cervical disc replacement

“…Nevertheless, plain radiographic assessment remains the front-line patient assessment tool for cTDR [ 12 , 16 ]. Previous studies have underscored the need for classification of radiographic changes around cTDR including heterotopic ossification (HO) [ 17 , 18 ] and bone loss [ 12 , 19 ]. Bone loss around orthopedic implants can result from sepsis [ 20 , 21 ], or aseptically due to bone adaptation or remodeling due to stress shielding (sometimes referred to as “Wolff’s law”) [ 22 ], osteoporosis [ 23 ], fluid pressure [ 24 ], as well as the well-described chronic inflammatory reaction to wear debris termed “osteolysis” in peripheral joint arthroplasty [ 19 ].…”