Effect of lumbar orthosis on intervertebral mobility. A roentgen stereophotogrammetric analysis.

To determine the stabilizing effect of external lumbar supports on the intervertebral mobility in the lower lumbar spine, seven patients with a posterolateral lumbosacral fusion without internal fixation were examined by roentgen stereophotogrammetric analysis in supine and erect positions 1 month after surgery, that is, after soft tissue healing but before fusion consolidation. Each patient was examined without lumbar support, with a molded, rigid orthosis and with a canvas corset with molded, plastic posterior support. Neither of the two types of lumbar support had any stabilizing effect on the sagittal, vertical, or transverse intervertebral translations. This study using roentgen stereophotogrammetric analysis confirms that lumbosacral orthosis has effect by restricting gross motions of the trunk rather than intervertebral mobility in the lumbar spine.     

Stability of lumbar fusion with transpedicular fixation determined by roentgen stereophotogrammetric analysis

STUDY DESIGN: An evaluation of the intervertebral stability of transpedicular instrumentation in posterolateral lumbar fusions by roentgen stereophotogrammetric analysis. OBJECTIVES: To determine the in vivo intervertebral stability of posterolateral lumbar fusions augmented with transpedicular screws and plates. SUMMARY OF BACKGROUND DATA: Transpedicular bone screw systems have been found to be as safe and clinically effective as other types of devices in stabilizing surgery of the spine. Many experimental studies have yielded basic data on the stabilizing implant effect in vitro, but the exact in vivo stabilizing effect on human lumbar vertebrae has not been presented previously. METHODS: In 12 patients, the intervertebral stability of posterolateral fusion in the lower lumbar spine augmented with transpedicular screws and plates was evaluated by serial roentgen stereophotogrammetric analysis with the patients in supine and erect positions 1 year after surgery. RESULTS: Screws in each fused vertebra yielded stable fixation or permitted sagittal intervertebral translations smaller than 1 mm induced by the positional change. A widely decompressed and destabilized vertebra without screw fixation yielded persisting intervertebral translations. CONCLUSIONS: The current study demonstrated the adequacy of in vivo stability of lumbar fusions augmented with transpedicular screws and plates. Sagittal translation seems easier to elicit than movements along the other three-dimensional axes. A widely decompressed and destabilized vertebra without screw fixation increases the risk for persisting intervertebral translations. The roentgen stereophotogrammetric analysis technique described seems to be a good way of comparing the in vivo behavior of different implant systems.     

Primary lumbosacral stability after open posterior and endoscopic anterior fusion with interbody implants: a roentgen stereophotogrammetric analysis

STUDY DESIGN: After posterior stabilization of the spondylolytic lumbosacral level, mobility of the fused vertebrae could be studied before and after an additional anterior endoscopic interbody fusion using roentgen stereophotogrammetric analysis. OBJECTIVE: To determine the in vivo primary lumbosacral stability of additional anterior interbody fusion after transpedicular screw fixation. SUMMARY OF BACKGROUND DATA: In vitro studies indicate a significant decrease in segmental motion after pedicle screw fixation and additional anterior fusion. Roentgen stereophotogrammetric studies demonstrate the adequacy of transpedicular lumbar instrumentation in posterolateral fusions. There are no studies examining the effect of additional anterior interbody fusion after posterior instrumentation in vivo. METHODS: In this study, 15 patients with low-grade spondylolisthesis at L5-S1 underwent a two-stage open posterior and endoscopic anterior lumbar fusion using carbon fiber (Brantigan I/F) cages. At surgery, tantalum markers were implanted into the fifth lumbar (L5) and the first sacral (S1) vertebra. All the patients were examined by roentgen stereophotogrammetric analysis after the first and second surgical procedures. RESULTS: After implantation of the posterior pedicle system only, the mean intervertebral mobility determined by roentgen stereophotogrammetric analysis was 0.23 mm in the transverse (x), 0.54 mm in the vertical (y), and 1.2 mm in the sagittal (z) axes. After additional anterior endoscopic fusion with carbon cages, the remaining translation between the fused segment L5/S1 decreased to 0.17 mm in the x, 0.16 mm in the y, and 0.44 mm in the z axes. CONCLUSION: Anterior endoscopic lumbosacral fusion significantly increases the primary stability of the posterior fusion with a pedicle system in two axes of motion.     

Posterolateral lumbar fusion using facet joint fixation with biodegradable rods: A pilot study

Roentgen stereophotogrammetric analysis (RSA) was used to assess whether there is a potential for biodegradable rods crossing the denuded facet joints to increase the stability and healing rate of lumbar posterolateral fusions. Eleven consecutive patients with lumbosacral disc/facet joint degeneration had a posterolateral fusion augmented with 2- or 3.2-mm biodegradable rods passing perpendicularly through the center of the denuded facet joints. The patients were followed-up with RSA in supine and erect positions monthly from the 2nd to the 6th postoperative month, and again 1 year postoperatively. All seven L5-S 1 fusions healed. Four cases were stable as defined by RSA within 3 months, two within 6 months, and one within 1 year. One L4-S1 fusion could not be evaluated by RSA. None of the remaining three L4-S1 fusions fully healed. In all three cases 1- to 3-mm intervertebral translations remained at 1 year. None of the 11 fusions showed any radiographic signs of osteolysis around the biodegradable rods. The promising results of this pilot study indicate that posterolateral L5-S 1 fusion augmented with transarticular biodegradable rods crossing the denuded facet joints may yield rapid intervertebral stabilization and a high healing rate without any adverse rod effects. This may be due to enhanced initial fusion stabilization and/or increased ossification induced by the rods.     

A method to evaluate the in vivo behaviour of lumbar spine implants

The aim of the study was to design a method for evaluating the stabilizing effect of different lumbar spine implants in vivo, and to apply this method to a comparison of plates versus rods in lumbar spine posterolateral fusion using transpedicular screw fixation. Fourteen patients, seven operated on with transpedicular plates and screws (VSP), and seven operated on with rods and screws (Diapason), matched according to number of levels fused, had tantalum markers inserted in the vertebrae at surgery, enabling roentgen stereophotogrammetric analysis (RSA). Mean patient age was 45 (range 33–56) years. In each group, two patients underwent fusion between L4 and L5, three between L5 and S1, and two from L4 to S1. In three patients, concomitant nerve root decompression was performed using a facet joint preserving technique. RSA was performed 4 weeks after surgery. This interval was chosen to allow enough time for soft tissue healing, but not fusion healing, to occur. RSA was performed in supine and standing position without any mobility provocation, in line with the postoperative regimen given. Movements between the outermost vertebrae of the fusion were calculated along the transverse, vertical and sagittal axes. The method of measurement along these three axes has previously been determined to be accurate to 0.3, 0.6 and 0.7 mm, respectively. One patient stabilized with rods and screws between L5 and S1 displayed a sagittal translation of 1.01 mm but no mobility along the transverse or vertical axes. In the remaining 13 patients, positional change from supine to standing did not provoke any intervertebral mobility above the RSA accuracy along any of the axes. With the limited provocation described, in line with the postoperative regimen for lumbar fusion patients, plates with transpedicular screws and rods with transpedicular screws both seem to give adequate intervertebral stability in posterolateral lumbar fusions. Received: 15 July 1998 Revised: 4 December 1999 Accepted: 4 February 2000     

Is there increased intervertebral mobility in isthmic adult spondylolisthesis? A matched comparative study using roentgen stereophotogrammetry

STUDY DESIGN: By roentgen stereophotogrammetric technique, the intervertebral mobility of the spondylolytic segment in eight patients was measured and compared with the mobility of eight nonspondylolytic patients matched according to sex, afflicted segment, and grade of disc degeneration. OBJECTIVES: To compare the intervertebral mobility of a spondylolytic segment with the mobility of a segment without spondylolysis in adult patients with back pain. SUMMARY OF BACKGROUND DATA: Evidenced by the resulting olisthetic deformity and supported by the outcome from prior investigations, spondylolysis is assumed to induce spinal segmental instability/hypermobility. METHODS: After percutaneous application of tantalum indicators for roentgen stereophotogrammetric technique, the intervertebral translations of the spondylolytic fifth lumbar vertebra were measured in eight adult patients with low back pain and low-grade olisthesis. Eight other patients without spondylolysis but with low back pain presumably on degenerative basis were chosen for comparison and had an identical measuring procedure using roentgen stereophotogrammetric technique. The two groups were matched in pairs according to sex, afflicted segment, and grade of disc degeneration. RESULTS: No significant difference was registered considering the intervertebral mobility for matched pairs in the two groups neither along the sagittal nor the vertical axis. The transverse translations were mostly negligible in both groups. CONCLUSION: The spondylolytic defect in pars interarticularis does not cause permanent instability/hypermobility detectable in the adult patient with low back pain and low-grade olisthesis.     

Knee motion after tibial osteotomy for arthrosis: Kinematic analysis of 7 patients

The in vivo kinematics of the knee in 7 patients with moderate medial gonarthrosis was analyzed before and 6 months after high tibial osteotomy using roentgen stereophotogrammetric analysis. The inclination of the femorotibial helical axis of rotation did not change with knee flexion or after surgery. The femorotibial rotation increased after surgery. No consistent change in patellar position after surgery was found. Patella translated laterally as the knee was flexed with a maximum patellar translation of about 15 mm and rotated internally with a maximum patellar internal rotation of about 15°. There was no significant change in patellar translation or rotation after surgery. There was a good concordance regarding the size of the tibial wedge removed during surgery, calculated from the Hip-Knee-Ankle radiographs and from the roentgen stereophotogrammetric measurements.     

Use of the anterior interbody fresh-frozen femoral head allograft in circumferential lumbar fusions

Many studies in the literature have documented the outcome of circumferential lumbar fusions. However, no study has specifically evaluated the performance of the anterior fresh-frozen femoral head allograft as a structural interbody graft material. All office and hospital records, including charts and radiographs, were reviewed to obtain pertinent clinical and radiographic information. The cases included 23 single-level fusions, 22 two-level fusions, and 5 fusions of three or more levels. In all, 88 fusion levels were analyzed radiographically. The mean follow-up time was 28 months (range, 24 to 36 months). All procedures were performed in a single stage. At the latest follow-up, clinical outcome was graded good to excellent in 39 (78%) cases, fair in 8 (16%) cases, and poor in 3 (6%) cases. The average time to anterior radiographic fusion was 6 months (range, 4 to 8 months). The overall fusion rate was 98%. The average preoperative anterior disk space height was 10 mm, 14 mm immediately after operation, and 13 mm at follow-up. The posterior disk space height averaged 5 mm before operation, 7 mm immediately after operation, and 6 mm at follow-up. The average segmental lordosis was 7 degrees before operation, 10 degrees immediately after operation, and 10 degrees at follow-up. Late postoperative disk space collapse of 3 mm or more was noted in 17% of the fused disk spaces examined. Seventy-eight percent of the disk spaces maintained a disk space height greater than that of their preoperative value at the latest follow-up. Segmental lordosis did not change significantly at follow-up. The occurrence of collapse did not correlate with the clinical result, smoking history, or surgical indication (p < 0.05). Perioperative complications included one pleural effusion, two urinary tract infections, and one deep wound infection. Late complications included five painful graft sites and two patients with pseudarthrosis. Fresh-frozen femoral head allograft fulfills its desired function as an anterior structural graft in combination with rigid posterior transpedicular fixation, maintaining the disk space height achieved at surgery while reliably allowing remodeling and incorporation into a solid anterior fusion.     

扩大PLIF治疗腰椎退行性疾病疗效分析

目的探讨扩大腰椎后路椎间融合术(posterior lumbar interbody fusion,PLIF)、cage椎间融合器结合椎弓根钉内固定治疗腰椎退行性疾病的临床疗效。方法回顾性分析我院2008年2月～2010年11月采用扩大PLIF、cage椎间融合器结合椎弓根钉内固定治疗腰椎退行性疾病66例患者的临床资料,其中男性19例,女性47例,平均年龄51(35～82)岁;腰椎间盘突出症21例,腰椎滑脱13例,腰椎管狭窄症32例,行单节段融合48例,行双节段融合18例。通过术前、术后及末次随访时X线片对比,对融合率、对JOA评分及椎间高度变化进行评估。结果本组66例均获随访,随访时间平均18(12～27)个月。所有患者症状消失或显著改善,无术后并发症发生。63例发生椎间融合,融合率达95.5%,其余3例未获得融合。术前、术后1周及术后12月以上末次随访时JOA评分分别为(13.4±3.2)分、(21.2±3.5)分及(23.3±3.8)分,融合节段椎间隙平均高度分别为(7.6±2.8)mm、(11.0±1.6)mm及(10.3±1.5)mm,术后1周及术后末次随访JOA评分、融合节段椎间隙平均高度与术前比较差异均有统计学意义(P<0.05),而术后不同时点间JOA评分、椎间隙平均高度比较差异无统计学意义(P>0.05)。结论扩大PLIF避免了过度牵拉可能造成神经根和硬膜囊的损伤,cage椎间融合器加椎弓根钉内固定行椎间融合治疗腰椎退行性疾病,可有效恢复椎间高度,提高融合率,是一种有效的治疗方法。     

经椎间孔入路腰椎体间融合内固定术的临床研究

目的：探讨经椎间孔入路腰椎体间融合内固定术的疗效。方法：回顾经椎间孔入路腰椎体间融合内固定术40例,共融合49个节段。分析比较术前及术后1年患者椎体间高度、角度、ODI、VAS评价、融合情况和并发症。结果：所有病例获随访,平均18个月,无严重并发症发生。手术时间平均160min,失血量平均510ml。依据ODI评分标准：优28例,良7例,可5例,椎间融合率100％。术后1年ODI和VAS均较术前明显减少（P〈0．01）,椎间高度、角度均明显增加（P〈0．05）。15例末次随访时仍后遗一定程度的腰痛。结论：经椎间孔入路腰椎体间融合内固定术可达到满意的椎间融合率和临床效果,特别适用于再次手术病例。     

Adjacent segment hypermobility after lumbar spine fusion: no association with progressive degeneration of the segment 5 years after surgery

Background and purpose Increased intradiscal pressure and relative segmental hypermobility are in vitro observations supporting the idea of increased postoperative load being a reason for progressive degeneration of the free mobile segment adjacent to a lumbar fusion. These mechanisms have been difficult to confirm in clinical studies, and an alternative theory claims instead that the adjacent segment degeneration follows a natural degenerative course in patients who are predisposed. We examined 9 patients 5 years after lumbar fusion, to assess whether relative hypermobility of the segment adjacent to fusion could be correlated to progressive degeneration of the same segment.

Patients and methods The 9 patients, all of whom had been treated with a lumbar fusion after a preoperative intervertebral mobility assessment by spinal RSA, were re-examined 5 years after surgery. The intervertebral translations of the vertebra proximal to the fusion were determined by RSA and compared to the mobility of the same lumbar segment before fusion. The disc height and any progressive reduction at the two levels proximal to the one fused were measured on conventional radiographs.

Results Adjacent segment mobility 5 years after fusion—expressed as mean transverse, vertical, and sagittal translation of the vertebra proximal to fusion— was not significantly changed compared to the mobility measured before surgery. Increased mobility of the segment seen in 5 individual patients was not associated with progressive degeneration of the same segment or to a poor clinical outcome.

Interpretation Hypermobility of the segment adjacent to fusion is not a general finding. Increased mobility that can be seen in certain individuals does not impair the 5-year result. The significance of mechanical alterations in adjacent segment degeneration is uncertain, and it is possibly overestimated.     

Adjacent segment hypermobility after lumbar spine fusion: No association with progressive degeneration of the segment 5 years after surgery

Background and purpose?Increased intradiscal pressure and relative segmental hypermobility are in vitro observations supporting the idea of increased postoperative load being a reason for progressive degeneration of the free mobile segment adjacent to a lumbar fusion. These mechanisms have been difficult to confirm in clinical studies, and an alternative theory claims instead that the adjacent segment degeneration follows a natural degenerative course in patients who are predisposed. We examined 9 patients 5 years after lumbar fusion, to assess whether relative hypermobility of the segment adjacent to fusion could be correlated to progressive degeneration of the same segment.

Patients and methods?The 9 patients, all of whom had been treated with a lumbar fusion after a preoperative intervertebral mobility assessment by spinal RSA, were re-examined 5 years after surgery. The intervertebral translations of the vertebra proximal to the fusion were determined by RSA and compared to the mobility of the same lumbar segment before fusion. The disc height and any progressive reduction at the two levels proximal to the one fused were measured on conventional radiographs.

Results?Adjacent segment mobility 5 years after fusion—expressed as mean transverse, vertical, and sagittal translation of the vertebra proximal to fusion— was not significantly changed compared to the mobility measured before surgery. Increased mobility of the segment seen in 5 individual patients was not associated with progressive degeneration of the same segment or to a poor clinical outcome.

Interpretation?Hypermobility of the segment adjacent to fusion is not a general finding. Increased mobility that can be seen in certain individuals does not impair the 5-year result. The significance of mechanical alterations in adjacent segment degeneration is uncertain, and it is possibly overestimated.     

前路和后路腰椎椎体间融合内固定术治疗下腰椎不稳的对比研究

目的 对比评价前路和后路腰椎椎体间融合内固定术治疗下腰椎不稳的效果.方法 将45例下腰椎不稳分为两组,前路手术组11例,后路手术组34例,分别行前路或后路腰椎体间融合内固定术,随访分析疗效、融合情况和并发症,测量和比较手术前后病人ODI、VAS和椎体间高度、角度.结果 患者获平均15个月随访,无严重并发症发生.前路组平均手术时间90 min,平均失血量180 ml,疗效优良率为90.9%,椎问融合率100%.后路组平均手术时间170 min,平均失血量470 ml,疗效优良率为85.3%,椎间融合率100%.两组术后1年ODI和VAS均较术前明显减少(P<0.01),椎间高度、角度均明显增加(P<0.05).两组间的术前及术后1年ODI、VAS、椎间高度、角度等指标无明显差异(P>0.05);前路组较后路组手术时间和出血量明显减少(P<0.05).结论 前路和后路腰椎体间融合内固定术治疗下腰椎不稳均可达到满意的椎间融合率和临床效果,前路腰椎体间融合内固定术手术时间和出血量较少.     

The radiological outcome of lumbar spinal fusion using a South African-developed dynamic spinal fixation system.

OBJECTIVES: To investigate the radiological outcome of the use of a new Cape Town-developed spinal fixation system. DESIGN: One hundred and fifty-five patients underwent posterior lumbar spinal fusions with this fixation system and autogenous bone graft more than a year ago. Of these 121 were available for radiological follow-up. SETTING: Spinal pedicle fixation systems are in common use in spinal fusion surgery. Most systems use rigid screws with a high rate of implant failure. In South Africa most spinal implants are imported and expensive, and this prompted the development of a locally manufactured dynamic spinal fixation system with the aim of producing a cheaper and more effective system with a lower risk of implant failure. OUTCOME MEASURES: A visual assessment of 1-year post-surgery radiographs by a qualified independent observer looking particularly at the rate of fusion and the incidence of implant failure. RESULTS: Bone fusion rates were comparable to all other pedicle fixation systems but implant failure rates were considerably less than in systems using rigid screws and more comparable to a similar dynamic spinal fixation system. CONCLUSIONS: This spinal fixation system is safe and effective in aiding bone fusion. It has a low rate of implant failure and is currently cheaper than all imported spinal fixation systems. It has therefore achieved the objectives that prompted its inception.     

改良腰椎板截骨回植治疗失稳性腰椎间盘突出症

目的：评价改良腰椎板截骨回植在失稳性腰椎间盘突出症中的疗效。方法：2009年3月至2011年8月对63例失稳性腰椎间盘突出症的患者行髓核摘除＋椎间融合＋椎弓根螺钉内固定＋改良腰椎板截骨回植手术,男33例,女30例;年龄22～68岁,平均48．4岁;病程3个月～13年,平均38．8个月。患者均有不同程度的腰腿疼痛,x线片、CT及MR检查诊断为失稳性腰椎间盘突出症。观测手术前后ODI和JOA评分、并发症发生率、影像学回植椎板愈合率及腰腿痛复发率。结果：62例患者切口I期愈合,1例11期愈合,无下肢深静脉血栓及椎间隙感染等并发症出现。61倒获1年或以上随访,平均随访时间33个月。术中神经损伤发生2例,硬膜囊损伤发生1例;术后1年回植椎板愈合58例：腰痛复发4例,腿痛复发1例。术后2周、6、12个月的ODI及JOA评分显著优于术前（P〈0．05）。结论：改良椎板截骨回植术治疗失稳性腰椎间盘突出症具有较低的术中神经硬膜囊损伤率和腰腿痛复发率、较高的椎板愈合率和较好的临床评分,是一种安全、有效的新方法,为临床失稳性腰椎间盘突出症手术开辟了一种新的术式。     

Mechanical loosening of total hip prostheses. A radiographic and roentgen stereophotogrammetric study

Twenty patients were examined by standard radiography and roentgen stereophotogrammetric analysis (RSA) during a two-year period after total hip arthroplasty. Eleven of the acetabular components migrated cranially and three femoral components migrated distally. This migration was most rapid during the first four months after operation. Our findings support the possibility that mechanical loosening is initiated by thermal injury during polymerisation of the cement; the less frequent migration of the metallic femoral component compared with the polyethylene acetabular component may be because the metal acts as a heat sink. Standard radiographs were inadequate for assessment of early mechanical loosening, whereas RSA could reveal migration within four months of the arthroplasty.     

Anterior cervical fusion using dense cancellous allografts and dynamic plating

OBJECTIVE: Dense cancellous grafts provide an open matrix for vascular and cellular penetration for early osseous integration. Thus, they provide a better biological fusion substrate than cortical or corticocancellous grafts. The aim of this study is to evaluate the efficacy of the dense cancellous allografts as a substrate for anterior cervical fusion along with instrumentation. METHODS: This is a retrospective study of 98 patients who underwent anterior cervical discectomy, fusion with dense cancellous allograft bone, and instrumentation using dynamic plating between January 2001 and March 2002. Of these procedures, 60 involved single-level and 38 involved two-level fusions. Subsidence was assessed by plain x-rays at 1, 3, 6, and 12 months and fusion at 3, 6, and 12 months after surgery. Fusion was defined as the appearance of bridging trabecular bone and absence of motion in flexion-extension films. RESULTS: The mean follow-up period was 15 months (range, 12-25 mo). Successful fusion was observed in 70, 84, and 96% of the patients at 3, 6, and 12 months, respectively. The average subsidences for single-level and two-level fusions were 2.0 and 3.2 mm, respectively. No allograft- or hardware-related complications were encountered in our series. CONCLUSION: Dense cancellous allografts are very effective as bone graft substitutes for achieving anterior cervical fusion along with instrumentation. Successful fusion was observed in 70% of our patients at 3 months, with a fusion rate of 96% at 1 year. These allografts provide an effective replacement for autologous grafts in cervical interbody fusion.     

Rationale for Interbody Fusion With Threaded Titanium Cages at Cervical and Lumbar Levels. Results on 357 Cases

Summary ? Study Design. Retrospective analysis of 357 cases of degenerative disc disease treated by interbody fusion with threaded titanium cages.  Objective. To determine the safety and efficiency of cervical and lumbar interbody fusions using threaded titanium cages and autogenous bone.  Summary of Background Data. Stabilizing the anterior column by interbody fusion, though reported over 50 years ago, is less commonly done than posterior fusions. The recent development of rigid cages housing autogenous bone simplifies the technique of interbody fusion. This report shows our combined results using this technique.  Materials and Methods. One hundred thirty-five patients had cervical fusions at 175 levels between C3 and C7. Two hundred twenty-two patients had lumbar fusion at 243 levels between L2 and S1. All surgeries involved one or two disc spaces except for one three level cervical fusion. We implanted all disc spaces with threaded cages containing autogenous bone.  Results. In the cervical area, 95% of the radiculopathic patients had a good to excellent result, but only 50% of the myelopathic patients did so. At lumbar level, 80% of the patients were classified as good to excellent, 15% improved but remained disabled, 5% had minimal or no improvement. The cervical fusion rate was 90% at 6 months and 100% at one year. Lumbar fusion rate was 91% at one year and 96% at 2 years. No late breakage or cage displacement occurred.  Conclusions. Cervical and lumbar interbody fusions with threaded titanium cages appear to be efficacious with few complications. Long term follow-up (4 years cervical, 7 years lumbar) confirms that impression.     

Roentgen stereophotogrammetric analysis of metal-backed hemispherical cups without attached markers

A method for the detection of micromotion of a metal-backed hemispherical acctabular cup is presented and tested. Unlike in conventional roentgen stereophotogrammetric analysis, the cup does not have to be marked with tantalum markers: the micromotion is calculated from the contours of the hemispherical part and the base circle of the cup. In this way two rotations (tilt and anteversion) and the translations along the three cardinal axes are obtained. In a phantom study, the maximum error in the position of the cup's centre was 0.04 mm. The mean error in the orientation of the cup was 0.41 with a 95% confidence interval of 0.28-0.54°. The in vivo accuracy was tested by repeated measurement of 21 radiographs from seven patients. The upper bound of the 95% tolerance interval for the translations along the transversal, longitudinal, and sagittal axes was 0.09. 0.07. and 0.34 mm. respectively: for the rotation, this upper bound was 0.39°. These results show that the new method, in which the position and orientation of a metal-backed hemispherical cup is calculated from its projected contours, is a simple and accurate alternative to attaching markers to the cup.     

A randomized prospective study of posterolateral lumbar fusion. Outcomes with and without pedicle screw instrumentation

STUDY DESIGN: A prospective evaluation of the clinical and radiographic outcomes of 71 patients who underwent lumbar fusion, with or without transpedicular instrumentation. The patients completed a questionnaire that determined pain relief, medication use, return to work, and overall satisfaction with surgery. OBJECTIVES: To explore the effect, if any, of instrumentation on the outcome of lumbar fusion surgery, according to reports of the patients, and whether there is a correlation between the radiographic determination of a solid fusion and the same patient-reported outcome. SUMMARY OF BACKGROUND DATA: The literature on this topic reports pseudarthrosis rates from 0% to 57% and good to excellent results from 56% to 95%. These studies provide no clear-cut recommendations concerning the effect of added lumbar instrumentation on patient-reported outcome in a prospective manner using concurrent control subjects. METHODS: The patients were randomized to groups with and without instrumentation after deciding to undergo a lumbar fusion and consenting to enter the study. Radiographs were obtained and questionnaires filled out at 6 weeks, 6 months, 1 year, and 2 years after surgery. RESULTS: There was no statistical difference in patient-reported outcome between the two groups. There was a slight nonsignificant trend toward increased radiographic fusion rate in the group with instrumentation that did not correlate with an increased patient-reported improvement rate. CONCLUSIONS: These results do not provide data that indicate a benefit in outcome from added instrumentation in elective lumbar fusions.