Tobias Pitzen

Anterior cervical plate stabilization in one- and two-level degenerative disease: overtreatment or benefit?

This consecutive case retrospective chart review of 356 patients compares the reoperation rate of one- and two-level anterior cervical discectomies for degenerative disease with and without anterior cervical plate stabilization (ACPS). A total of 210 patients underwent surgery without ACPS (bone alone) and 146 patients underwent surgery with the addition of ACPS. Follow-up ranged from 1 to 9 years. A total of 22 patients with one- or two-level cervical arthrodesis required a second surgical intervention (19 bone alone, 3 with ACPS). Reoperations were performed in the bone-alone group for pseudarthrosis in 12 cases and for progression of degenerative disease in 7 cases. The reoperations in the ACPS group were performed for pseudarthrosis in one case and settling of the graft with screw fracture before fusion in two cases. The log-rank test, which uses all patients and their total follow-up periods, was statistically significant in favoring ACPS (p = 0.05). Furthermore, the reoperation rate after 1 year was also significantly lower when ACPS was utilized compared with bone alone (p = 0.0308, Fishers exact test, two tailed). These data provide evidence that the addition of ACPS in one- and two-level cervical degenerative disease does not constitute overtreatment but rather supplements the internal stabilization initially provided by the bone graft and yields a lower reoperation rate.

Reoperation in patients after anterior cervical plate stabilization in degenerative disease.

Study Design. Consecutive case retrospective chart review. Objectives. First, to assess whether the number of patients requiring a second cervical surgical intervention was changed as a result of using anterior cervical plate stabilization, and second, to determine the additional risks and/or benefits associated with the hardware implantation. Summary of Background Data. The optimal technique of performing stabilization, arthrodesis, and alignment of a cervical segment after discectomy with neural decompression in degenerative disease has yet to be determined. Methods. The charts of 402 patients who had undergone an anterior cervical discectomy and arthrodesis for degenerative disease performed both with and without anterior cervical plate stabilization were reviewed, and reoperation data were compiled. The average follow‐up time was 3.8 years (range, 1.5‐9.4 years). Results. Of 365 patients with 1‐ or 2‐level cervical arthrodesis, 22 required a second surgical intervention (20 bone alone, 2 with anterior cervical plate stabilization). The Log‐Rank test, which uses all patients and their total follow‐up periods, was statistically significant favoring anterior cervical plate stabilization at one and two levels (P = 0.015). Conclusions. The addition of anterior cervical plate stabilization in one‐ and two‐level cervical degenerative disease supplements the internal stabilization initially provided by the bone graft, and yields a lower reoperation rate.

Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study.

Study Design. Prospective, controlled, randomized, multicenter study. Objective. To analyze implant complications and speed. Summary of Background Data. Rigid plate designs, in which the screws are locked to the plate, are in common use and thought to provide more fixation than dynamic designs, in which the screws may glide when the graft is settling. The aim of the study is to analyze (1) implant complications, (2) speed of fusion, (3) loss of lordosis, and (4) clinical outcome in both types of plates. Methods. One hundred thirty-two patients were included and assigned by randomization to one of the groups in which they received a routine anterior cervical discectomy and autograft fusion with either a dynamic plate (ABC, study group) or a rigid plate (CSLP, control group). At discharge, after 3 and 6 months and finally after 2 years, implant complications, segmental mobility, absence of radiolucencies, absence of bone sclerosis, evidence of bridging trabecular bone, loss of lordosis, Visual Analog Scale (VAS) and Neck Disability Score were recorded. All radiographic measurements were performed by an independent radiologist. Results. There have been 4 patients with implant complications within the control group and no implant complications within the study group, P = 0.045. Mean segmental mobility before discharge for the study group was 1.7 mm, 1.4 mm after 3 months, 0.8 mm after 6 months, and 0.4 mm after 2 years. For the control group, these values were 1.0, 1.8, 1.6, and 0.5 mm. The difference at 6 months between both groups was significant (P = 0.024). Neither absence of radiolucencies, nor absence of sclerosis, nor evidence of bridging bone showed significant differences between the 2 groups through the postoperative follow-up (P > 0.05). The loss of segmental lordosis for the study group with respect to intraoperative radiograph was 1.3° at discharge and 4.3° after 2 years. For the controlgroup, these values were 0.9°, 0.7°. The difference at 2 years was significant (P = 0.003). Clinical postoperative outcome (VAS and ODI) was not different between the 2 groups through the postoperative follow-up (P > 0.05). Conclusion. Dynamic cervical plate designs provide less implant complications (no patient) compared with rigid plate designs (4 patients). Speed of fusion was faster in the presence of a dynamic plate. However, loss of segmental lordosis is significantly higher if dynamic plates are used, which did not result in differences regarding clinical outcome between dynamic and constrained plates after 2 years. Thus, dynamic plates should be considered to be the preferred treatment option because of the lower risk for implant failure-related revision surgery.

The Prodisc-c Prothesis: Clinical and Radiological Experience 1 Year After Surgery

Study Design. This is a prospective randomized and controlled study, approved by the local ethical committee of Saarland (Germany). Objective. The aim of the current study was to analyze segmental motion following artificial disc replacement using disc prosthesis over 1 year. A second aim was to compare both segmental motion as well as clinical result to the current gold standard (anterior cervical discectomy and fusion [ACDF]). Summary of Background Data. ACDF may be considered to be the gold standard for treatment of symptomatic degenerative disc disease within the cervical spine. However, fusion may result in progressive degeneration of the adjacent segments. Therefore, disc arthroplasty has been introduced. Among these, artifical disc replacement seems to be promising. However, segmental motion should be preserved. This, again, is very difficult to judge and has not yet been proven. Methods. A total of 49 patients with cervical disc herniation were enrolled and assigned to either study group (receiving a disc prosthesis) or control group (receiving ACDF, using a cage with bone graft and an anterior plate). Roentgen stereometric analysis (RSA) was used to quantify intervertebral motion immediately as well as 3, 6, 12, 24, and 52 weeks after surgery. Also, clinical results were judged using visual analog scale and neuro-examination at even RSA follow-up. Results. Cervical spine segmental motion decreased over time in the presence of disc prosthesis or fusion device. However, the loss segmental motion is significantly higher in the fusion group, when looked at 3, 6, 12, 24, and 52 weeks after surgery. We observed significant pain reduction in neck and arm after surgery, without significant difference between both groups. Conclusion. Cervical spine disc prosthesis remains cervical spine segmental motion within the first 1 year after surgery. The clinical results are the same when compared with the early results following ACDF.

The radiographic failure of single segment anterior cervical plate fixation in traumatic cervical flexion distraction injuries.

Study Design. A radiographic review of 87 patients with either unilateral or bilateral facet dislocations or fracture/dislocations treated with anterior cervical discectomy, fusion, and plating. Objective. The primary objective of this study was to report the incidence of radiographic failure and factors that would predispose to this loss of alignment. The secondary objective was to report the rate of pseudarthrosis. Summary of Background Data. Biomechanical and clinical data conflict regarding the appropriate approach and method of fixation of distractive flexion cervical injuries. Unilateral and bilateral facet fracture subluxations may be surgically stabilized by anterior cervical discectomy, fusion, and plating, posterior instrumentation, or both. There are no documented reports of the rate of radiographic failure of this procedure when limited to a single level injury from a distractive flexion mechanism. Methods. Inclusion criteria were all single-level unilateral and bilateral facet fracture dislocations or subluxations treated with a single-level anterior cervical discectomy, fusion, and plating. Retrospectively, 107 cases were identified (87 with complete radiographs) from January 1994 to December 2001. Radiographic failure was defined as a change in translation of greater than 4 mm and/or change in angulation of greater than 11° between the immediate postoperative films and the most recent follow-up. Fusion was assessed radiographically. Results. A 13% incidence of radiographic loss of alignment is reported in 87 unilateral and bilateral facet fracture subluxations stabilized with anterior cervical discectomy, fusion, and plating. Radiographic failure correlated with the presence of endplate compression fracture and facet fractures on injury radiographs. There was no correlation between radiographic failure and age, gender, surgeon, unilateral or bilateral injury, plate type, level of injury, degree of translation, or sagittal alignment at the time of injury. Conclusion. Loss of postoperative alignment occurred in 13% of facet fracture subluxations treated with anterior cervical discectomy, fusion, and plating. Concern regarding mechanical failure of flexion/distraction injuries should be high when they are associated with fractures of either the facets or of the endplate. Endplate fracture was associated with both mechanical failure and pseudarthrosis.

Anterior cervical plate fixation: a biomechanical study to evaluate the effects of plate design, endplate preparation, and bone mineral density.

Study Design. A biomechanical study using multidirectional flexibility testing in a human cadaveric cervical spine model of a flexion-distraction injury. Objectives. To compare the immediate postoperative stabilizing effect of dynamic and rigid anterior cervical plates and to assess the confounding effects of bone mineral density (BMD) and endplate preparation technique. Summary of Background Data. Dynamic plate designs presumably increase load sharing between the plate and graft, but their effect on spinal stabilization has not been assessed in a traumatic flexion-distraction model. Methods. Twenty-four fresh frozen human cervical functional spinal units were dual-energy x-ray absorptiometry scanned for bone mineral density and allocated into 4 groups by the type of plate, dynamic (ABC, Aesculap, Germany) versus rigid (Cervical Spine Locking Plate, Synthes USA, Paoli, PA), and the technique of endplate preparation, intact versus removed. Each functional spinal unit had all posterior ligaments transected and both inferior facets excised, after which anterior discectomy, grafting, and plating was performed. Nondestructive testing applied a 1.5 Nm pure moment, whereas ranges of motion and neutral zones were measured in flexion/extension, lateral bending, and rotation. Ratios of the range of motion and neutral zone of the plated to the intact site were analyzed. The load sharing between the plate and the functional spinal unit was measured via strain gauges mounted on the plate. Results. There were no significant differences in the range of motion or neutral zone ratios between the 2 plate designs, except for the range of motion ratio in extension, where the dynamic plate exhibited better stabilization than the rigid plate (P = 0.02). There was a consistent interaction whereby endplate removal resulted in better stabilization for the dynamic plate, but less stabilization for the rigid plate. Significantly less motion was observed with increasing bone mineral density in all loading directions. In flexion and extension, the dynamic plate measured one-third less strain than the rigid plate. Conclusions. The dynamic plate appeared to provide better stabilization in extension, and the technique of endplate preparation has some effect on immediate stabilization, dependent on the type of plate employed. Bone mineral density of the specimen was a strong determinant of the degree of stabilization achieved, regardless of the type of plate used.

Motion of threaded cages in posterior lumbar interbody fusion

Abstract A high rate of pseudarthrosis and a high overall rate of implant migration requiring surgical revision has been reported following posterior lumbar interbody fusion using BAK threaded cages. The high rate of both pseudarthrosis and implant migration may be due to poor fixation of the implant. The purpose of this study was to analyse the motion of threaded cages in posterior lumbar interbody fusion. Six cadaveric human lumbar spine segments (three L2/3 and three L4/5 segments) were prepared for biomechanical testing. The segments were tested, without preload, under forces of axial compression (600 N), torsion (25 Nm) and shearing force (250 N). The tests were performed first with the segments in an intact state, and subsequently following instrumented stabilisation with two BAK cages via a posterior approach. These results were compared with those of a finite element model simulating the effects of identical forces on the segments with constructs. As the results were comparable, the finite element model was used for analysing the motion of BAK cages within the disc space. Motion of the implants was not seen in compression. In torsion, a rolling motion was noted, with a range of motion of 10.6° around the central axis of the implant when left/right torsion (25 Nm) was applied. The way the implants move within the segment may be due to their special shape: the thread of the implants can not prevent the BAK cages rolling within the disc space.

Evaluation of a new monocortical screw for anterior cervical fusion and plating by a combined biomechanical and clinical study.

Abstract The purpose of this combined study was to evaluate the stability and safety of a new monocortical screw-plate system for anterior cervical fusion and plating (ACFP) according to Caspar in comparison with classical bicortical fixation. In the biomechanical part of the study two groups, each comprising six fresh human cadaveric spines (C4–C7), matched for bone mineral density, additionally resulting in almost the same mean age, were used. Range of motion and neutral zone were analyzed in flexion-extension, rotation (left, right) and lateral bending (left, right) using pure moments of ± 2.5 Nm for each specimen in the intact state, after discectomy at C5/6 and after discectomy at C 5/6 followed by bone grafting plus plating (Caspar plates), with either monocortical or bicortical screws. For all three motion planes, no significant difference could be found between the new monocortical and the bicortical fixation techniques. The clinical part of the study was performed as a prospective study on 30 patients suffering from symptomatic degenerative cervical disc disease in one segment. At the latest follow-up, no hardware- or graft-related complications were seen in any of the patients. Following these findings monocortical screw fixation can be recommended for the majority of anterior cervical fusion and plating procedures in degenerative disease, making the procedure quicker, easier, and safer. Bicortical screw fixation still has specific indications for multilevel stabilization, poor bone quality (osteoporosis, rheumatoid disease – as bicortical oversized rescue screw), unstable spines (trauma, tumour) and in particular for the realignment of kyphotic deformities (restoration of the normal lordotic curve). Due to the design of the study the results apply only to surgical treatment of monosegmental degenerative disc disease at the time.

Comparison of bioresorbable and titanium plates in cervical spinal fusion: early radiologic and clinical results.

Study Design This is a prospective, randomized, and controlled study, approved by the local ethical committee of Saarland (Germany), no. 209/06. Objective The aim of this study was to compare clinical results, segmental motility, magnetic resonance imaging (MRI) compatibility, and change of the bone density of a cervical spine segment that was treated with either bioresorbable or titanium plates in single level. Summary and Background Data Anterior cervical discectomy and fusion including plate fixation is an accepted technique for treatment of symptomatic degenerative disc disease. Titanium plates have been used but cause imaging artifacts. Radiolucent bioresorbable plates and screws were developed to reduce the imaging artifacts associated with titanium. Methods Forty patients with single level cervical radiculopathy were randomized to anterior discectomy and fusion with bioresorbable plate (19 patients, study group) or titanium plate (18 patients, control group). Follow-up used a visual analog scale (VAS) with regard to brachial pain and Neck Disability Index (NDI) for neck pain. Radiostereometry was performed immediately postoperative and after 6 weeks, 3, and 6 months. MRI of the cervical spine was obtained immediately postoperatively at 3 and 6 months to assess hematoma, infection, and swelling. Computed tomography of the operated cervical spine segment was performed to assess bone density, expressed in Hounsfield units. Results Three-dimensional analysis of segmental motion (medio-lateral, cranio-caudal and anterior-posterior) did not reveal any statistical difference between both groups at any time postoperatively (P>0.05). Fusion rate and speed evaluated on Radiostereometric analysis and computed tomography of cervical spine segment were similar in both groups. MRI of cervical spine did not show any pathology, especially hematoma and infection. The VAS and NDI did not differ between both groups after 6 months (P>0.05). Conclusions Anterior plate fixation by using a bioresorbable plate has the same fusion progress and stability as titanium. During the study, no complications like soft tissue swelling and infection occurred.

Variation of endplate thickness in the cervical spine

The purpose of the study was to investigate possible variation of thickness of the cervical spine endplate with respect to endplate orientation (superior or inferior endplate) and level distribution (C4–C7). Six human cervical spine segments C4–C7 were used to create six specimen of C4, C5, C6, and C7, respectively. The bony endplates of each vertebra were cleaned carefully from disc tissue without damaging the endplates. Six endplates with severe degenerative changes were excluded from the study. The posterior elements were removed, and a midaxial cut using a bone saw was performed through each vertebral body, thus producing a superior and inferior half. Each half-vertebra was then glued onto a piece of wood with the endplate oriented upwards and horizontally. For each specimen, four computed tomography scans were taken and thickness of the endplate was measured at five points on each scan perpendicular to the midaxial cut. Factorial analysis of variance (ANOVA) and Scheffe-test were used to detect significant differences. All peripheral regions were significantly thicker than the central point of the endplate if all measuring points were considered for statistical analysis, regardless of scan, endplate orientation or level (Scheffe-test, P<0.001). In both superior and inferior endplates, peripheral areas were thicker than the central region (Scheffe-test, P<0.001). For all levels, the endplate within the peripheral regions was thicker than within the central region and the difference reached significance for the superior and inferior endplate of C4, C5, and C6 and the inferior endplate of C7 (Scheffe-test, P<0.05). The peripheral regions of the cervical spine endplate are usually thicker than its central region, regardless of endplate orientation and level (C4, C5, C6, C7) distribution.