The influence of tibial morphology on the design of an anatomical tibial baseplate for TKA.

BACKGROUND: Finding the right balance between tibial coverage and minimal implant overhang is an important factor in TKA. Another significant cause of failure is component malrotation. METHODS: An average master shape of the proximal tibia at TKA resection level was calculated using fine slice computed tomographies of 117 cadaveric knees. To find out whether alternate implant contours would be necessary depending on the patient's body size, we established five subgroups to compare. CAD-Analysis was performed to simulate the overhang produced after ±4°/±7°/±10° rotation. RESULTS: A master shape for the tibial resection cut (with a 5° posterior slope, 7 mm under lateral joint line) could be determined. Neither left vs. right knee joint, nor male vs. female nor the size subdivision appears to alter the calculated master shape significantly. The optimized shape allowing for ±4° of rotational freedom was found to be the best variant. CONCLUSIONS: Valid methods have been obtained to design a two-dimensional average shape of the tibial plateau. The modifications described in this study might come in useful, when designing future implant designs. CLINICAL RELEVANCE: An optimized fit at the tibial plateau and lower rates of component malrotation may result in better outcomes after TKA.

Development and validation of a quantitative method to assess pedicle screw loosening in posterior spine instrumentation on plain radiographs.

PURPOSE: Currently, the diagnosis of pedicle screw (PS) loosening is based on a subjectively assessed halo sign, that is, a radiolucent line around the implant wider than 1 mm in plain radiographs. We aimed at development and validation of a quantitative method to diagnose PS loosening on radiographs. METHODS: Between 11/2004 and 1/2010 36 consecutive patients treated with thoraco-lumbar spine fusion with PS instrumentation without PS loosening were compared with 37 other patients who developed a clinically manifesting PS loosening. Three different angles were measured and compared regarding their capability to discriminate the loosened PS over the postoperative course. The inter-observer invariance was tested and a receiver operating characteristics curve analysis was performed. RESULTS: The angle measured between the PS axis and the cranial endplate was significantly different between the early and all later postoperative images. The Spearman correlation coefficient for the measurements of two observers at each postoperative time point ranged between 0.89 at 2 weeks to 0.94 at 2 months and 1 year postoperative. The angle change of 1.9° between immediate postoperative and 6-month postoperative was 75% sensitive and 89% specific for the identification of loosened screws (AUC = 0.82). DISCUSSION: The angle between the PS axis and the cranial endplate showed good ability to change in PS loosening. A change of this angle of at least 2° had a relatively high sensitivity and specificity to diagnose screw loosening.

Radiographic and safety details of vertebral body stenting: results from a multicenter chart review.

BACKGROUND: Up to one third of BKP treated cases shows no appreciable height restoration due to loss of both restored height and kyphotic realignment after balloon deflation. This shortcoming has called for an improved method that maintains the height and realignment reached by the fully inflated balloon until stabilization of the vertebral body by PMMA-based cementation. Restoration of the physiological vertebral body height for pain relief and for preventing further fractures of adjacent and distant vertebral bodies must be the main aim for such a method. A new vertebral body stenting system (VBS) stabilizes the vertebral body after balloon deflation until cementation. The radiographic and safety results of the first 100 cases where VBS was applied are presented. METHODS: During the planning phase of an ongoing international multicenter RCT, radiographic, procedural and followup details were retrospectively transcribed from charts and xrays for developing and testing the case report forms. Radiographs were centrally assessed at the institution of the first/senior author. RESULTS: 100 patients (62 with osteoporosis) with a total of 103 fractured vertebral bodies were treated with the VBS system. 49 were females with a mean age of 73.2 years; males were 66.7 years old. The mean preoperative anterior-middle-posterior heights were 20.3-17.6-28.0 mm, respectively. The mean local kyphotic angle was 13.1°. The mean preoperative Beck Index (anterior edge height/posterior edge height) was 0.73, the mean alternative Beck Index (middle height/posterior edge height) was 0.63. The mean postoperative heights were restored to 24.5-24.6-30.4 mm, respectively. The mean local kyphotic angle was reduced to 8.9°. The mean postoperative Beck Index was 0.81, the mean alternative one was 0.82. The overall extrusion rate was 29.1%, the symptomatic one was 1%. In the osteoporosis subgroup there were 23.8% extrusions. Within the three months followup interval there were 9% of adjacent and 4% of remote new fractures, all in the osteoporotic group. CONCLUSIONS: VBS showed its strengths especially in realignment of crush and biconcave fractures. Given that fracture mobility is present, the realignment potential is sound and increases with the severity of preoperative vertebral body deformation.

Comparative effectiveness research across two spine registries.

BACKGROUND: Comparative effectiveness research in spine surgery is still a rarity. In this study, pain alleviation and quality of life (QoL) improvement after lumbar total disc arthroplasty (TDA) and anterior lumbar interbody fusion (ALIF) were anonymously compared by surgeon and implant. METHODS: A total of 534 monosegmental TDAs from the SWISSspine registry were analyzed. Mean age was 42 years (19-65 years), 59% were females. Fifty cases with ALIF were documented in the international Spine Tango registry and used as concurrent comparator group for the pain analysis. Mean age was 46 years (21-69 years), 78% were females. The average follow-up time in both samples was 1 year. Comparison of back/leg pain alleviation and QoL improvement was performed. Unadjusted and adjusted probabilities for achievement of minimum clinically relevant improvements of 18 VAS points or 0.25 EQ-5D points were calculated for each surgeon. RESULTS: Mean preoperative back pain decreased from 69 to 30 points at 1 year (ØΔ 39pts) after TDA, and from 66 to 27 points after ALIF (ØΔ 39pts). Mean preoperative QoL improved from 0.34 to 0.74 points at 1 year (ØΔ 0.40pts). There were surgeons with better patient selection, indicated by lower adjusted probabilities reflecting worsening of outcomes if they had treated an average patient sample. ALIF had similar pain alleviation than TDA. CONCLUSIONS: Pain alleviation after TDA and ALIF was similar. Differences in surgeon's patient selection based on pain and QoL were revealed. Some surgeons seem to miss the full therapeutic potential of TDA by selecting patients with lower symptom severity.

Safety, effectiveness and predictors for early reoperation in therapeutic and prophylactic vertebroplasty: short-term results of a prospective case series of patients with osteoporotic vertebral fractures.

INTRODUCTION: Vertebroplasty (VP) is a cost-efficient alternative to kyphoplasty; however, regarding safety and vertebral body (VB) height restoration, it is considered inferior. We assessed the safety and efficacy of VP in alleviating pain, improving quality of life (QoL) and restoring alignment. METHODS: In a prospective monocenter case series from May 2007 until July 2008, there were 1,408 vertebroplasties performed during 319 interventions in 306 patients with traumatic, lytic and osteoporotic fractures. The 249 interventions in 233 patients performed because of osteoporotic vertebral fractures were analyzed regarding demographics, treatment and radiographic details, pain alleviation (VAS), QoL improvement (NASS and EQ-5D), complications and predictors for new fractures requiring a reoperation. RESULTS: The osteoporotic patient sample consisted of 76.7% (179) females with a median age of 80 years. A total of 54 males had a median age of 77 years. On average, there were 1.8 VBs fractured and 5 VBs treated. The preoperative pain was assessed by the visual analog scale (VAS) and decreased from 54.9 to 40.4 pts after 2 months and 31.2 pts after 6 months. Accordingly, the QoL on the EQ-5D measure (-0.6 to 1) improved from 0.35 pts before surgery to 0.56 pts after 2 and to 0.68 pts after 6 months. The preoperative Beck Index (anterior height/posterior height) improved from a mean of 0.64 preoperative to 0.76 postoperative, remained stable at 2 months and slightly deteriorated to 0.72 at 6 months postoperatively. There were cement leakages in 26% of the fractured VBs and in 1.4% of the prophylactically cemented VBs; there were symptoms in 4.3%, and most of them were temporary hypotension and one pulmonary cement embolism that remained asymptomatic. The univariate regression model revealed a tendency for a reduced risk for new or refractures on radiographs (OR = 2.61, 95% CI 0.92-7.38, p = 0.12) and reoperations (OR = 2.9, 95% CI 0.94-8.949, p = 0.1) when prophylactic augmentation was performed. The final multivariate regression model revealed male patients to have an about three times higher refracture risk (radiographic) (OR = 2.78, p = 0.02) at 6 months after surgery. Patients with a lumbar index fracture had an about three to five times higher refracture/reoperation risk than patients with a thoracic (OR = 0.33/0.35, p = 0.009/0.01) or thoracolumbar (OR = 0.32/0.22, p = 0.099/0.01) index fracture. CONCLUSION: If routinely used, VP is a safe and efficacious treatment option for osteoporotic vertebral fractures with regard to pain relief and improvement of the QoL. Even segmental realignment can be partially achieved with proper patient positioning. Certain patient or fracture characteristics increase the risk for early radiographic refractures or new fractures, or a reoperation; a consequent prophylactic augmentation showed protective tendencies, but the study was underpowered for a final conclusion.

The International Documentation and Evaluation System IDES: a single center observational case series for development of an ankle prosthesis documentation questionnaire and study of its feasibility and face validity.

BACKGROUND: The number of implanted total ankle replacements is increasing and most articles present short- and mid-term results. Comparison of outcomes is difficult because of inconsistent terminology and different use of parameters. MATERIALS AND METHODS: We created a module for total ankle prostheses in the framework of the International Documentation and Evaluation System (IDES). Content development was conducted with an iterative process based on a single surgeon series of 74 HINTEGRA(c) total ankle replacements and expert opinions. RESULTS: The IDES ankle module comprises three forms A, B and C for recording of primary (A), revision (B) and followup (C) procedures. 74 primary interventions, 28 revisions and 92 followups could be documented in detail with the final version of the questionnaires. CONCLUSION: The IDES-forms facilitate a structured and standardized data collection for total ankle arthroplasties. Implemented on the academic MEMdoc portal http://www.memdoc.org of the University of Bern, all registered users can make use of IDES in its online or paper based versions.

SWISSspine-a nationwide health technology assessment registry for balloon kyphoplasty: methodology and first results.

BACKGROUND CONTEXT: The Swiss Federal Office of Public Health demanded a nationwide health technology assessment registry for cervical and lumbar total disc arthroplasty and for balloon kyphoplasty (BKP) to make a decision about reimbursement of these interventions. PURPOSE: The goal of the SWISSspine registry is to generate evidence about the safety and effectiveness of these technologies. We report on results of patients with balloon kyphoplasty. STUDY DESIGN/SETTING: Prospective, multicenter, observational case series. PATIENT SAMPLE: From March 2005 until June 2008, 331 interventions with 391 treated levels in 320 patients have been documented. 75.6% of patients were females with mean age of 74 years (range 43-95.2 years); mean age of males was 72.6 years (range 41.4-93 years). OUTCOME MEASURES: Surgeon-administered outcome instruments were primary intervention form for BKP, implant, and follow-up form; patient self-reported measures were Euroqol-5D, North American Spine Society, and a comorbidity questionnaire. METHODS: Data were recorded perioperative, at 3 months, 1 year, and annually thereafter. Wilcoxon signed-rank test was used for comparison of preoperative to postoperative measurements. Multivariate regression was used for identifying factors with a significant influence on the outcome. RESULTS: Significant and clinically relevant reduction of back pain, improvement of quality of life (QoL), and reduction of pain killer consumption were seen in the 1-year follow-up. Improvement of preoperative segmental kyphosis was achieved in the majority of cases. There were three symptomatic cement extrusions with radiculopathy documented. CONCLUSIONS: Balloon kyphoplasty is a safe and effective treatment concerning pain reduction, QoL improvement, and pain killer consumption. The SWISSspine registry proved to be an excellent tool for evaluation of this new technology, and its results, in combination with an elaborate health technology assessment report, led to a permanent coverage of BKP by the basic health insurance.

Safety and efficacy of vertebroplasty: Early results of a prospective one-year case series of osteoporosis patients in an academic high-volume center.

BACKGROUND: Vertebroplasty (VP) is a cost-efficient alternative to kyphoplasty. However, it is considered inferior when it comes to maintaining safety and in vertebral body (VB) height restoration. We assess the safety and efficacy of VP in alleviating pain, improving quality of life (QoL), and restoring alignment. MATERIALS AND METHODS: In a prospective monocenter case series, from April 2007 until July 2008, 1,422 vertebroplasties were performed, during 307 interventions, in 279 patients with traumatic, lytic, and osteoporotic fractures with 28 repeat interventions, for new fractures after the primary surgery, in 28 patients. The 226 interventions (n=203 patients) done for osteoporotic fractures were analyzed for demographics, treatment and radiographic details, pain alleviation, QoL improvement [NASS and Euroqol (EQ-5D)] and complications. RESULTS: Osteoporotic patient sample consisted of 77.8% (n=158) females with a median age of 78 years and 45 males who had the same median age. Around 69% of these patients were ASA (American Society of Anesthesiologists) grade 3 and above. On an average there were 1.8 VBs fractured and five VBs treated,whereas the most frequently performed cementations were in six (35.6%, n=80) or five (19.6%, n=44) levels. About 36.5%, (n=414) of the interventions were localized at the thoraco-lumbar junction (Th12-L2). On applying the Genant classification, there was a slight height reduction in 13.1% (n=29), a medium loss in 34.3% (n=78), and a severe loss of height in 52.6% (n=119). The pre-operative pain was assessed by the visual analog scale (VAS) and decreased from 56.7 to 41.4 pts after two months. Accordingly, the QoL on the EQ-5D measure (0.6 to 1) improved from 0.32 pts before surgery to 0.58 pts after two months. The pre-operative Beck index (anterior height/posterior height) improved from a mean of 0.66 preoperative to 0.80 post-operative and remained stable at two months post-operatively. There were cement leakages in 33% of the fractured VBs and in 0.8% of the prophylactically cemented VBs; there were symptoms in 7.1%, and most of them were temporary hypotension and one pulmonary cement embolism that remained asymptomatic. CONCLUSION: If routinely used, VP is a safe and efficient treatment option for osteoporotic vertebral fractures with regard to pain relief and improvement of the QoL. Even segmental re-alignment can be achieved to a certain extent with proper patient positioning.