Adjacent Segment Mechanics in Cervical Arthrodesis Patients

This study aims to determine to what extent patient-specific factors, iatrogenic factors, and biomechanical factors influence cervical spine mechanics after single-level and two-level arthrodesis.

Study Overview

• Status: Completed
• Conditions: Intervertebral Disc Degeneration
• Intervention / Treatment: Procedure: C5-C6 arthrodesis

Detailed Description

The etiology of adjacent segment pathology following cervical fusion remains highly controversial. Adjacent segment disease is believed to result from one or more of the following distinct causes:

1. the natural history of the adjacent disc;
2. disruption of the adjacent segment anatomy due to the initial surgery; and
3. biomechanical stress on the adjacent level following the fusion.

The long-term goal of our research is to reduce or prevent symptomatic adjacent segment degeneration in the spine. The overall hypothesis of this study is that adjacent segment kinematics (i.e. translations, rotations, helical axis of motion) and arthrokinematics (i.e. disc deformation and facet joint surface interactions) after ACDF are determined primarily by patient-specific anatomy and iatrogenic factors, and not by increased biomechanical stress due to the fusion.

A prospective longitudinal study is proposed to determine to what extent patient-specific factors (Specific Aim 1), iatrogenic factors (Specific Aim 2), and altered biomechanics (Specific Aim 3) affect dynamic cervical spine function following fusion. Participants will be C56 (n=22) and C67 (n=22) single-level fusion patients, C456 (n=22) and C567 (n=22) two-level fusion patients, and asymptomatic controls similar in age to the fusion patients (n=22). Patients will be tested prior to surgery, one year post-surgery, and three years post-surgery. At each test, participants will complete clinical questionnaires to assess pain and function, and they will perform full range of motion flexion\extension and axial rotation of the head and cervical spine while biplane radiographs are recorded at 30 images per second. A highly accurate and validated volumetric model-based tracking process and custom data analysis software will be utilized to determine intervertebral kinematics (i.e. translations, rotations, helical axis of motion) and arthrokinematics (i.e. disc deformation and facet joint surface interactions) at each test session.

This prospective study will identify the factors that have the greatest effect on adjacent segment mechanics after cervical fusion. If the hypotheses are confirmed, this will provide support for increased attention to patient-specific factors and surgical technique. Alternatively, if the results indicate that adjacent segment mechanics are influenced primarily by increased stress after arthrodesis, this will provide support for increased attention to the design of motion-sparing devices.

• Study Type: Observational
• Enrollment (Actual): 106

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15203
      • University of Pittsburgh Biodynamics Lab

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 17 years to 56 years (Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

All patients will be between 21 and 60 years of age and will be scheduled to undergo single-level or two-level anterior cervical discectomy and fusion (ACDF) at the C56, C67, C456 or C567 levels. Indications for surgical intervention will be progressive symptoms refractory to conservative treatment for myelopathy, radiculopathy, or myeloradiculopathy resulting from degenerative spondylosis, symptomatic cervical disc herniation, or symptomatic disc degeneration.

Description

Inclusion Criteria:

• Patients must agree to return for all follow-up visits and provide informed consent.
• Control subjects will be asymptomatic, with no injury or disease that will interfere with spine function, such as previous spine surgery or trauma.

Exclusion Criteria:

• Participants will have no other injury or disease that will interfere with spine function, such as previous spine surgery or trauma
• Individuals who have been previously clinically diagnosed with poor bone quality and those who do not intend to stay in the Pittsburgh area for a period of at least 3 years post-surgery will be excluded.
• Females who are pregnant or plan to be pregnant within 3 years of surgery will be excluded.

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Prospective

Number of groups / cohorts

5

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Asymptomatic Controls; Individuals who have no history of neck pain, trauma or surgery, similar in age and sex to the surgical patients
C5-C6 arthrodesis; Patients scheduled to undergo C5-C6 anterior cervical arthrodesis	Procedure: C5-C6 arthrodesis; A standard Smith Robinson anterior medial approach to the cervical spine. Vertebral endplates will be prepared by removing the cartilage endplate. Tricortical anterior iliac crest autografts will be harvested with a low-speed oscillating saw. Allografts will be fresh-frozen, vacuum-sealed, nonradiated tricortical grafts. All grafts will be fashioned in a typical Smith-Robinson formation. The motion segment will be distracted approximately 2-mm beyond the graft height before the insertion of each graft. Fusion plate will be contoured to cervical lordosis. Cervical plates will be positioned using surgical midline markers. All rigid anterior plate fixations will be performed using titanium anterior fixed-angle screw systems.
C6-C7 arthrodesis; Patients scheduled to undergo C6-C7 anterior cervical arthrodesis	Procedure: C5-C6 arthrodesis; A standard Smith Robinson anterior medial approach to the cervical spine. Vertebral endplates will be prepared by removing the cartilage endplate. Tricortical anterior iliac crest autografts will be harvested with a low-speed oscillating saw. Allografts will be fresh-frozen, vacuum-sealed, nonradiated tricortical grafts. All grafts will be fashioned in a typical Smith-Robinson formation. The motion segment will be distracted approximately 2-mm beyond the graft height before the insertion of each graft. Fusion plate will be contoured to cervical lordosis. Cervical plates will be positioned using surgical midline markers. All rigid anterior plate fixations will be performed using titanium anterior fixed-angle screw systems.
C4-C5-C6 arthrodesis; Patients scheduled to undergo C4-C5-C6 anterior cervical arthrodesis	Procedure: C5-C6 arthrodesis; A standard Smith Robinson anterior medial approach to the cervical spine. Vertebral endplates will be prepared by removing the cartilage endplate. Tricortical anterior iliac crest autografts will be harvested with a low-speed oscillating saw. Allografts will be fresh-frozen, vacuum-sealed, nonradiated tricortical grafts. All grafts will be fashioned in a typical Smith-Robinson formation. The motion segment will be distracted approximately 2-mm beyond the graft height before the insertion of each graft. Fusion plate will be contoured to cervical lordosis. Cervical plates will be positioned using surgical midline markers. All rigid anterior plate fixations will be performed using titanium anterior fixed-angle screw systems.
C5-C6-C7 arthrodesis; Patients scheduled to undergo C5-C6-C7 anterior cervical arthrodesis	Procedure: C5-C6 arthrodesis; A standard Smith Robinson anterior medial approach to the cervical spine. Vertebral endplates will be prepared by removing the cartilage endplate. Tricortical anterior iliac crest autografts will be harvested with a low-speed oscillating saw. Allografts will be fresh-frozen, vacuum-sealed, nonradiated tricortical grafts. All grafts will be fashioned in a typical Smith-Robinson formation. The motion segment will be distracted approximately 2-mm beyond the graft height before the insertion of each graft. Fusion plate will be contoured to cervical lordosis. Cervical plates will be positioned using surgical midline markers. All rigid anterior plate fixations will be performed using titanium anterior fixed-angle screw systems.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Kinematics	range of motion (ROM) in degrees	pre-surgery to 3 years post-surgery
Iatrogenic factors	adjacent segment disc height and sagittal alignment; graft height, plate placement	pre-surgery to 3 years post-surgery
Kinematics	The helical axis of motion (HAM)	pre-surgery to 3 years post-surgery
Kinematics	The continuous 3D intervertebral kinematics (translations and rotations).	pre-surgery to 3 years post-surgery
Arthrokinematics	Disc deformation	pre-surgery to 3 years post-surgery
Arthrokinematics	Facet joint capsule deformation	pre-surgery to 3 years post-surgery

Collaborators and Investigators

• Sponsor: University of Pittsburgh
• Investigators: Principal Investigator: William Anderst, PhD, University of Pittsburgh

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2016
• Primary Completion (Actual): December 30, 2024
• Study Completion (Actual): December 30, 2024

Study Registration Dates

• First Submitted: February 10, 2016
• First Submitted That Met QC Criteria: January 19, 2017
• First Posted (Estimated): January 23, 2017

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: February 3, 2025
• Last Verified: September 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Spinal Diseases; Intervertebral Disc Degeneration
• Other Study ID Numbers: STUDY19070070

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• product manufactured in and exported from the U.S.: No