Sagittal cervical alignment after cervical disc arthroplasty and anterior cervical discectomy and fusion: results of a prospective, randomized, controlled trial.
ABSTRACT Radiographic results of a multicenter, prospective randomized study comparing 1-level cervical total disc replacement (TDR-C) with anterior cervical discectomy and fusion (ACDF).
To evaluate the effect on device-level lordosis, cranial and caudal adjacent level lordosis, and overall cervical sagittal alignment (C2-C6) after TDR-C or ACDF.
Cervical total disc replacement (TDR-C) has emerged as a promising alternative to ACDF in a select group of patients. The maintenance and/or improvement of sagittal balance is essential in preserving functionality after reconstructive spinal procedures. Recent studies have documented changes in spinal alignment after TDR-C, however, no studies have compared these changes to those noted in matched group of patients that have undergone ACDF.
Radiographic data were obtained from the randomized group of a multicenter, randomized, prospective, controlled study comparing TDR-C (ProDisc-C, Synthes Spine, West Chester, PA) with ACDF in the treatment of 1-level cervical disc disease. Complete radiographic data were available for 89 TDR-C patients (average age: 42.2 years) and 91 ACDF patients (average age: 41.7 years). Cervical lordosis at the device level, cranial and caudal adjacent levels, and total cervical lordosis (C2-C6) were independently measured before surgery and 2 years after surgery using custom image stabilization software (Quantitative Motion Analysis, Medical Metrics, Inc, Houston, TX).
C5-C6 was the most common operative level (TDR-C: 54%; ACDF: 55%). At 2 years after surgery, the TDR-C group experienced statistically significant changes in lordosis of 3.0 degrees (P < 0.001), 0.90 degrees (P = 0.006), and -1.9 degrees (P < 0.001) at the operative, cranial, and caudal adj-acent levels, respectively. ACDF experienced changes in lordosis of 4.2 degrees (P < 0.001), 1.0 degrees (P = 0.001), and -1.5 degrees (P = 0.001), respectively. The between-group differences were significant at the operative level (P = 0.03) and the caudal adjacent level (P = 0.05). Total cervical lordosis increased in both TDR-C and ACDF by 3.1 degrees and 3.8 degrees , respectively (P = 0.49).
In both TDR-C and ACDF, lordosis increased at the device-level, cranial adjacent level, and in total cervical lordosis, while lordosis decreased at the caudal adjacent level. Although ACDF facilitated a greater increase in device level lordosis (+1.25 degrees ) and less loss of lordosis at the caudal adjacent level compared with TDR-C (-0.39 degrees ), the clinical relevance of the small differences remain unknown.
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ABSTRACT: Cervical total disc replacement has emerged as a surgical option to preserve motion and potentially avoid adjacent-segment disease after anterior cervical discectomy and fusion. Recently, much attention has been directed at the ability of a given device to maintain and/or restore normal segmental alignment. Nonphysiological disc and segmental angulation could result in increased stresses transmitted to the facet joints and posterior elements, conflicting with the essence of arthroplasty and potentially leading to adjacent-segment disease. The goal of this study was to contrast device alignment and segmental kinematics provided by 3 different cervical disc prostheses. Sixty patients were retrospectively analyzed and divided into 3 groups receiving the Bryan, ProDisc-C, or Synergy disc. Only single-level arthroplasty cases were included in the study. Lateral dynamic radiographs of the cervical spine were analyzed using quantitative motion analysis software (Medical Metrics, Inc.) to analyze the kinematics at the index level both preoperatively and postoperatively. Several parameters were noted, including range of motion, disc angles, shell angles, anterior and posterior disc heights, translation, and center of rotation. Preoperative and postoperative data were compared using the Student t-test with a significance level of p < 0.05. Postoperatively, all 3 disc groups maintained adequate range of motion at the implanted level. With respect to the shell angles, the Synergy disc demonstrated the least variability, maintaining 6 degrees lordotic configuration between the device endplates. In the Bryan disc group, significant shell kyphosis developed postoperatively (p < 0.0001). Both ProDisc-C and Synergy discs significantly increased anterior and posterior disc heights (p < 0.0001). The Bryan and Synergy discs maintained the natural center of rotation, whereas significant anterior shift occurred with ProDisc-C. The goal for motion preservation at the implanted level was achieved using all 3 devices. The Synergy disc was unique in its ability to alter device angulation by 6 degrees. The Bryan disc demonstrated device endplate kyphosis. Both the Synergy disc and ProDisc-C increased disc space height.Neurosurgical FOCUS 06/2010; 28(6):E6. DOI:10.3171/2010.3.FOCUS1058 · 2.14 Impact Factor
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ABSTRACT: Anterior cervical discectomy and fusion had been considered a safe and effective procedure for radiculopathy and myelopathy in the cervical spine, but degeneration in adjacent spinal levels has been a problem in some patients after fusion. Since 2002, cervical disc arthroplasty has been established as an alternative to fusion. The objective of this study was to review data concerning the role of cervical arthroplasty in reducing adjacent-level degeneration. A systematic review was performed using the MEDLINE, EMBASE, Cochrane, and LILACS databases, focusing on a structured question involving the population of interest, types of intervention, types of control, and outcomes studied. No study has specifically compared the results of arthroplasty with the results of fusion with respect to the rate of postoperative development of adjacent-segment degenerative disease. One paper described a rate for adjacent-level surgery. The level of evidence of that paper was classified 2b, and although its authors found a statistically significant between-groups difference (arthroplasty vs fusion) using log-rank analysis, re-analysis according to number needed to treat (in the current paper) did not reveal statistical significance. Adjacent-level degeneration has not been adequately studied in a review of the available randomized controlled trials on this topic, and there is no clinical evidence of reduction in adjacent-level degeneration with the use of cervical arthroplasty.Neurosurgical FOCUS 06/2010; 28(6):E5. DOI:10.3171/2010.3.FOCUS1032 · 2.14 Impact Factor
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ABSTRACT: Benchtop biomechanics study examining kinematic effects of progressive resection in a human cadaveric spine model. To determine the effects of posterior longitudinal ligament (PLL) resection, unilateral and bilateral foraminotomy, and laminectomy on cervical intervertebral rotation and translation after cervical disc arthroplasty (CDA). Although the clinical results after CDA have been studied, there remain unanswered questions regarding the surgical techniques used at the time of device insertion. For example, it is unclear whether a surgeon should retain or resect the PLL and uncinate processes at the time of primary surgical intervention. Further, the effect of a subsequent posterior decompression (foraminotomy or laminectomy) on the stability of a motion segment containing a disc arthroplasty is unknown. Three-dimensional intervertebral motion was measured by biplanar videography in human cadaveric spines at C4-C5 or at C5-C6 subjected to a 1.5-Nm moment applied to induce motion in the sagittal plane. Coupled motions were not constrained. After measuring intact spine motion, disc arthroplasty with bilateral ventral foraminotomy was performed without PLL resection. Sequentially, rotations and translations were measured after PLL resection, unilateral foraminotomy, bilateral foraminotomy, and laminectomy. CDA with bilateral ventral foraminotomy increased sagittal rotation by 0.4 degrees (16%) compared with the intact spine. The addition of PLL resection increased rotation by 0.5 degrees (14% increase). Unilateral and bilateral foraminotomy had negligible effects on sagittal rotation or anteroposterior (AP) translation. Laminectomy resulted in an additional sagittal plane rotation of 2 degrees. The sagittal-plane interverterbal rotation resultant after all interventions was 6 degrees , with 1.5 mm of AP translation occurring only. Given that a greater degree of motion was seen with PLL resection combined with ventral foraminotomy, we recommend that PLL resection be performed when performing CDA. In our benchtop model, unilateral and bilateral posterior foraminotomies were not associated with the creation of significant sagittal rotational or AP translational instability.Spine 08/2010; 35(18):1676-83. DOI:10.1097/BRS.0b013e3181c55bcd · 2.45 Impact Factor