The effect of posterior decompressive procedures on segmental range of motion after cervical total disc arthroplasty.

STUDY DESIGN: We quantified the segmental biomechanics of a cervical total disc replacement (TDR) before and after progressive posterior decompression. We hypothesized that posterior decompressive procedures would not significantly increase range of motion (ROM) at the index TDR level. OBJECTIVE: To quantify the kinematics of a cervical total disc replacement (TDR) before and after posterior cervical decompression. SUMMARY OF BACKGROUND DATA: A reported yet unaddressed issue is the potential for the development of same-segment disease after implantation of a cervical TDR and the implications of same-segment posterior decompression on TDR mechanics. METHODS: Eight human cadaveric cervical spines C3-C7 were tested in flexion-extension, lateral bending, and axial rotation while intact, after C5-C6 TDR, C5-C6 unilateral foraminotomy, C5-C6 bilateral foraminotomies, and after C5 laminectomy in combination with the bilateral foraminotomies. Moment versus angular motion curves were obtained for each testing step, and the load-displacement data were analyzed to determine the range of angular motion for each step. RESULTS: Unilateral foraminotomy did not result in a statistically significant increase in flexion-extension ROM, and did not increase the ROM to a degree greater than normal. Although bilateral foraminotomies did increase flexion-extension ROM, motion remained within a physiological range. A full laminectomy added to the bilateral foraminotomies significantly increased ROM and was also associated with distortion of the load-displacement curves. CONCLUSION: With respect to segmental biomechanics as demonstrated, we think that for same-segment disease, a unilateral foraminotomy can be performed safely. However, the impact of in vivo conditions was not accounted for in this model, and it is possible that cyclical loading and other physiological stresses on such a construct may affect the behavior and lifespan of the implant in a way that cannot be predicted by a biomechanical study. Bilateral foraminotomies would require close observation and additional clinical follow-up, whereas complete laminectomy combined with bilateral foraminotomies should be avoided after TDR given the significant changes in kinematics. In addition, future disc replacement designs may need to account for changes after posterior decompression for same-segment disease. LEVEL OF EVIDENCE: N/A.

Biomechanical effects of a unilateral approach to minimally invasive lumbar decompression.

Minimally invasive (MI) lumbar decompression became a common approach to treat lumbar stenosis. This approach may potentially mitigate postoperative increases in segmental motion. The goal of this study was to evaluate modifications to segmental motion in the lumbar spine following a MI unilateral approach as compared to traditional facet-sparing and non-facet sparing decompressions. Six human lumbar cadaveric specimens were used. Each specimen was tested in flexion-extension 0 N and 400 N of follower preload), axial rotation, and lateral bending. Each testing condition was evaluated following three separate interventions at L4-L5: 1) Minimally invasive decompression, 2) Facet-sparing, bilateral decompression, and 3) Bilateral decompression with a wide facetectomy. Range of motion following each testing condition was compared to intact specimens. Both MI and traditional decompression procedures create significant increases in ROM in all modes of loading. However, when compared to the MI approach, traditional decompression produces significantly larger increase in ROM in flexion-extension (p<0.005) and axial rotation (p<0.05). It additionally creates increased ROM with lateral bending on the approach side (p<0.05). Lateral bending on the non-approach side is not significantly changed. Lastly, wide medial facet removal (40% to 50%) causes significant hypermobility, especially in axial rotation. While both MI and traditional lumbar decompressions may increase post-operative ROM in all conditions, a MI approach causes significantly smaller increase in ROM. With an MI approach, increased movement with lateral bending is only toward the approach side. Further, non-facet sparing decompression is further destabilizing in all loading modes.

Biomechanical characteristics of an integrated lumbar interbody fusion device.

INTRODUCTION: We hypothesized that an Integrated Lumbar Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) plus posterior instrumentation (FIREBIRD, Orthofix, Lewisville, TX). Purpose of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA) can stabilize single motion segments as well as an anterior interbody spacer (PILLAR AL) + pedicle screw construct (FIREBIRD). METHODS: Eight cadaveric lumbar spines (age: 43.9±4.3 years) were used. Each specimen's range of motion was tested in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) under intact condition, after L4-L5 PILLAR SA with intervertebral screws and after L4-L5 360° fusion (PILLAR AL + Pedicle Screws and rods (FIREBIRD). Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload. RESULTS: Integrated fusion using the PILLAR SA device demonstrated statistically significant reductions in range of motion of the L4-L5 motion segment as compared to the intact condition for each test direction. PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR. A comparison between the PILLAR SA integrated fusion device versus 360° fusion construct with spacer and bilateral pedicle screws was statistically significant in FE and LB. The 360° fusion yielded motion of 1.0±0.5° in FE, 1.0±0.8° in LB (p0.05). CONCLUSIONS: The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws. The residual segmental motions compare very favorably with published biomechanical studies of other interbody integrated fusion devices.

Safety and effectiveness of retrorectal presacral approach for lumbosacral axial instrumentation. A clinical study.

This prospective study aimed to quantify the risks and complications associated with AxiaLIF in a series of 29 patients. AxiaLIF is a fusion technique using a percutaneous retrorectal, presacral corridor approach to access the L5-S1 and L4-L5 intervertebral spaces transaxially, through the body of S1 and L5 vertebrae. The fusion rate in the present series was 92% and the reported results ranged from 68% to 100%. The only serious complication in the authors' series was one presacral haematoma (1/29, or 35%). Symptomatic subsidence occurred in the stand alone group, resulting in foraminal stenosis and radiculopathy in two patients (7%) and back pain in one (3.5%). Painful radiolucent halo around the rod was noted in a spondylolytic case (1/29, or 3.5%); it resolved after transpedicular instrumentation. AxiaLIF is a novel truly minimally invasive technique not requiring blood transfusion and can be safely performed as a day surgery. Retroperitoneal haematoma, ureteral and vascular injuries can be avoided by respecting the regional anatomical landmarks as guided by accurate fluoroscopy. Only expanding haematomas may have to be drained. Bowel perforation can be prevented by gently sweeping away the rectum from the sacrum before inserting the guide probe.

The silicone ring tourniquet in orthopaedic operations of the extremities.

Tourniquets provide a bloodless field in limb operations and their introduction in orthopaedic operative technique has been considered as a landmark. A new tourniquet device, a silicone ring tourniquet (SRT) (HemaClear or S-MART, OHK Medical Devices, Haifa, Israel), was introduced into clinical practice a few years ago. A few clinical studies as well as comparative studies in volunteers have reported its use in a relatively small number of cases. The aim of this prospective study is to report the clinical use of this device in a large number of patients, including all possible applications of a tourniquet. The SRT was used in 536 cases including 337 male and 119 female patients with a mean age of 43.7 years (range 6 to 87 years). The average tourniquet time was 58.5 minutes (range 6 to 180 minutes). It was applied in 362 (67.5%) elective and in 174 (32.5%) trauma cases including fractures (n:109, 62.6%) and soft-tissue injuries (n:65, 37.4%). The most frequent application site was the femur (n:255, 47.6%), followed by the forearm (n:154, 28.7%), humerus (n:65, 12.1%), and calf (n:62, 11.6%). Because the device is sterile it was possible to use it in operations in which the pneumatic tourniquet cannot be used, such as open reduction and internal fixation of humeral shaft and femoral supracondylar fractures. In 14 patients (2.6%), the tourniquet failed intraoperatively, and the cause was an unexpected raised blood pressure. The SRT - with a pre-set pressure according to the size and the tension model - is easy to apply. It is sterile, and occupies a narrow area of the limb. Its application combines three functions at the same time: exsanguination, tourniquet, and stockinet application. Although it cannot entirely replace the classic pneumatic tourniquet, it is a safe and useful device in orthopaedic operations because of its advantages.