• Matti Scholz, Philipp Schleicher, Simone Pabst, and Frank Kandziora.
• *Center for Spinal Surgery and Neurotraumatology, BG-Hospital Frankfurt/Main, Germany; and †Schön Clinic Harthausen, Bad Aibling, Germany.
• Spine. 2015 Apr 1;40(7):E375-80.

Study DesignIn vitro biomechanical analysis of different multilevel cervical fixation techniques.ObjectiveTo compare the multilevel stability of a cervical anchored spacer (AS) with established fixation techniques.Summary Of Background DataTo avoid plate-related complications, for example, dysphagia zero-profile AS has been developed. The use of these new zero-profile implants for treatment of cervical degenerative disc disease is widely accepted after encouraging biomechanical results for single-level instrumentation. However, there is only little knowledge about the biomechanical stability of these zero-profile devices in multilevel instrumentations.MethodsEight fresh-frozen human cadaveric cervical spines (C3-C7) were nondestructively tested in a biomechanical 3-dimensional spine test setup. Segmental range of motion (ROM) under torsional load of 1.5 N·m was measured optoelectronically. Intact spine baseline measurement specimens were tested with 2- and 3-level instrumentation including (1) stand-alone PEEK-cage; (2) PEEK-cage plus locking plate; and (3) AS. Repeated-measures analyses of variance were used for statistical analysis.ResultsComparison of baseline ROM and stand-alone PEEK-cage instrumentation showed a significant lower segmental ROM only for 2-level instrumentations. Cage plus plate and AS were able to reduce segmental ROM significantly (P < 0.05) in 2- and 3-level instrumentations. Comparing cage plus plate and AS, a significant lower ROM was detected for flexion/extension in 2- and 3-level instrumentation and for lateral bending in 2-level instrumentation using cage plus plate.ConclusionSegmental stability decreases with the number of instrumented segments regardless of the used implant. Comparing the different fixation techniques biomechanically, the locking plate and cage construct was stiffer in all test modes than the anchored devices in multilevel constructs. However, it remains unclear what the clinical significance may be.Level Of EvidenceN/A.

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