Restoration of compressive loading properties of lumbar discs with a nucleus implant—a finite element analysis study

Background ContextDiscectomy is a common procedure for treating sciatica. However, both the operation and preceding herniated disc alter the biomechanical properties of the spinal segment. The disc mechanics are also altered in patients with chronic contained herniation. The biomechanical properties of the disc can potentially be restored with an elastomeric nucleus replacement implanted via minimally invasive surgery.PurposeThe purpose of this study was to determine whether the compressive characteristics of the intervertebral disc after a nucleotomy can be restored with an elastomeric nucleus replacement.Study DesignA finite element model of the L4–L5 intervertebral disc was created to investigate the effect of the implantation of an elastomeric nucleus replacement on the biomechanical properties of the disc under axial loading.MethodA L4–L5 physiologic intervertebral disc model was constructed and then modified to contain a range by volume of nucleotomies and nucleus replacements. The material properties of the nucleus replacement were based on experimental data for an elastomeric implant. The compressive stiffness, radial annular bulge, and stress distribution of the nucleotomy and nucleus replacement models were investigated under displacement-controlled loading.ResultsRemoval of nucleus pulposus from the physiologic disc reduced the force necessary to compress the disc 2 mm by 50%, altered the von Mises stress distribution, and reduced the outward radial annular bulge. Replacing the natural nucleus pulposus of the physiologic disc with an artificial nucleus reduced the force required to compress the disc 2 mm by 10%, indicating a restoration of disc compressive stiffness. The von Mises stress distribution and annular bulge observed in the disc with an artificial nucleus were similar to that observed in the physiologic disc.ConclusionThis study demonstrates that despite having different material properties, a nucleus replacement implant can restore the axial compressive mechanical properties of a disc after a discectomy. The implant carries compressive load and transfers the load into annular hoop stress.     

Acute Myeloid Leukemia With Myelodysplasia-Related Changes: A New Definition

Acute myeloid leukemia (AML) with multilineage dysplasia was introduced in the 2001 World Health Organization (WHO) classification to encompass cases of AML characterized by myelodysplastic syndrome–like features. The 2008 WHO classification revised this group into a new category, AML with myelodysplasia-related changes (AML-MRC). The category now includes patients with at least 20% blasts in peripheral blood or bone marrow and any of the following: (1) AML arising from a previous MDS or mixed MDS/myeloproliferative neoplasm, (2) AML with a specific MDS-associated cytogenetic abnormality and/or (3) AML with multilineage dysplasia. Up to 48% of all patients with AML are encompassed within the AML-MRC subgroup. AML-MRC patients have worse prognosis compared with patients with AML, not otherwise specified.     

Analysis of the Vertical Ground Reaction Forces and Temporal Factors in the Landing Phase of a Countermovement Jump

In most common bilateral landings of vertical jumps, there are two peak forces (F1 and F2) in the force-time curve. The combination of these peak forces and the high frequency of jumps during sports produce a large amount of stress in the joints of the lower limbs which can be determinant of injury. The aim of this study was to find possible relationships between the jump height and F1 and F2, between F1 and F2 themselves, and between F1, F2, the time they appear (T1 and T2, respectively) and the length of the impact absorption phase (T). Thirty semi-professional football players made five countermovement jumps and the highest jump of each player was analyzed. They were instructed to perform the jumps with maximum effort and to land first with the balls of their feet and then with their heels. All the data were collected using a Kistler Quattro Jump force plate with a sample rate of 500 Hz. Quattro Jump Software, v.1.0.9.0., was used. There was neither significant correlation between T1 and F1 nor between T1 and F2. There was a significant positive correlation between flight height (FH) and F1 (r = 0.584, p = 0.01) but no significant correlation between FH and F2. A significant positive correlation between F1 and T2 (r = 0.418, p < 0.05) and a significant negative correlation between F2 and T2 (r = -0.406, p < 0.05) were also found. There is a significant negative correlation between T2 and T (r = -0. 443, p < 0.05). T1 has a little effect in the impact absorption process. F1 increases with increasing T2 but F2 decreases with increasing T2. Besides, increasing T2, with the objective of decreasing F2, makes the whole impact absorption shorter and the jump landing faster.

Key points

• In the landing phase of a jump there are always sev-eral peak forces. The combination of these peaks forces and the high frequency of jumps during sports produces a large amount of stress in the joints of the lower limbs which can be determinant of injury.
• In the most common two-footed landings usually appear two peak forces (F1 and F2) in the force-time curve and the second one is usually related to injury’s risk. In this article it is shown that increasing the time F2 appears decrease F2.
• Increasing landing times could be counterproductive with respect to the goals of the sport. In this article it is shown that increasing the time F2 appears makes, however, the whole impact absorption shorter in du-ration.

Key words: Impact absorption, peak forces, vertical jump, injuries     

Predictive factors for cutting-out in femoral intramedullary nailing

BackgroundFemoral intramedullary nailing is currently one of the most frequent surgical treatments for extracapsular hip-fracture fixation. Cutting-out of the lag screw is the main complication of this technique, but only few studies have approached the cutting-out focussed on femoral nailing. The aim of this study was to confirm in patients treated with intramedullary nailing not only with regard to previous reports about the association of cutting-out with technical factors, but also with regard to clinical factors not previously studied.MethodsCase–control study of all patients sustaining a cut-out of the femoral nail was carried out and a control sample was randomly selected among all extracapsular hip-fracture patients during the study period (2005–2008). All clinical and technical variables were collected from medical records. Orthopaedic Trauma Association (AO/OTA) fracture classification, Singh Osteoporosis Index of the contralateral hip and the American Society of Anaesthesiology (ASA) criteria for preoperative clinical status were used. Statistical assessment included bivariant analysis and multivariant logistic regression analysis.ResultsA total of 916 hip-fracture cases were treated in the study period: 33 of them (3.6%) were identified as suffering cutting-out, and 315 controls fulfilling inclusion criteria were also recruited. No statistical differences were found in age, sex or other socio-demographic variables between the two groups. Bivariant analysis showed significant differences between groups in technical variables (tip-apex distance, suboptimal placement of lag screw, fracture diastasis, inadequate fixation quality and distal static locking) and in clinical variables (osteoporosis severity, right hip affected, better previous ability for walking and better preoperative ASA status). Multivariant logistic regression analysis showed significant association only for tip-apex distance and inadequate fixation quality. Differences in distal static locking were close to statistical significance.ConclusionsThe strongest predictor of cutting-out in femoral nailing is tip-apex distance. This study suggests that distal static locking and other clinical conditions play an important role in this fixation failure.     

Treatment of osteoporosis after liver transplantation with ibandronate

Osteoporosis is a major side‐effect after liver transplantation (LTX). Therefore, the objective of the study was to evaluate the efficacy of ibandronate to reduce fractures after LTX. Seventy‐four patients after LTX were included in the study and measurements of bone mineral density (BMD) of lumbar spine and proximal femur using dual energy X‐ray absorptiometry (DEXA) were performed prior to and 3, 6, 12 and 24 months after surgery. The study group (IBA) consisted of 34 patients who received calcium (1 g/day), vitamin D3 (800–1000 IE/day) and ibandronate 2 mg every 3 months intravenously for 1 year. The control group consisted of 40 patients (CON) who received calcium and vitamin D3 at the same dosages. Prevalence of new fractures was predefined as primary endpoint. Changes of BMD and biochemical markers of bone metabolism were also investigated. In all patients, we found a reduction of BMD in the first few months after LTX. In the lumbar spine and the proximal femur the maximum reduction occurred 3 and 6 months post‐LTX. One and 2 years after transplantation, the group receiving ibandronate demonstrated a better recovery from loss of BMD and a significantly lower prevalence of fractures (IBA 2 vs. CON 10 P < 0.04, χ²). Ibandronate with calcium and vitamin D3 reduces the BMD‐loss after LTX and decreases the rate of bone fractures significantly.     

Splenectomy improves survival by increasing arterial blood supply in a rat model of reduced‐size liver

Prevention of acute portal hyperperfusion in small‐for‐size livers by inflow modulation results in beneficial postoperative outcome. The objective of this study was to unravel the underlying mechanism, emphasizing the intimate relationship between portal venous (PV) and hepatic arterial (HA) blood flow (BF). Rats underwent partial hepatectomy (pHx), splenectomy before pHx or splenectomy and ligation of the A. hepatica before pHx. Portal venous blood flow (PVBF), hepatic arterial blood flow (HABF), and tissue pO₂ were assessed during stepwise resection from 30% to 90%. Hepatic regeneration and hypoxia‐responsive gene expression were analyzed in each group after nonlethal 85% pHx. 90% pHx caused a fourfold rise in PVBF, a slight decrease in HABF with a 50% reduction in pO₂, and high mortality. Splenectomy before pHx reduced the PVBF and caused a rise in HABF with doubling in tissue pO₂. An attenuation of hypoxia‐responsive gene expression turned into enhanced hepatocellular regeneration and improved survival. A. hepatica ligation abolished the beneficial effect of splenectomy on tissue oxygenation, proliferation, and outcome. In conclusion, the beneficial effect of splenectomy in small‐for‐size livers can be attributed to a rise in HABF with sufficient oxygen supply rather than to a reduced portal venous hyperperfusion to the remnant liver.     

Penile rehabilitation protocol after robot‐assisted radical prostatectomy: assessment of compliance with phosphodiesterase type 5 inhibitor therapy and effect on early potency

Study Type – Therapy (case series)
Level of Evidence 4

OBJECTIVE

To evaluate factors that affect compliance in men who enrol in a phosphodiesterase type 5 inhibitor (PDE5I) protocol after nerve‐sparing robot‐assisted prostatectomy (RAP), and report on short‐term outcomes, as PDE5Is may help restore erectile function after RAP and patient adherence to the regimen is a factor that potentially can affect outcome.

PATIENT AND METHODS

We prospectively followed 77 men who had nerve‐sparing RAP and enrolled in a postoperative penile rehabilitation protocol. The men received either sildenafil citrate or tadalafil three times weekly. The minimum follow‐up was 8 weeks. Potency was defined as erection adequate for penetration and complete intercourse. Compliance was defined as men adhering to the regimen for ≥2 months.

RESULTS

The mean age of the cohort was 57.8 years and the median follow‐up was 8 months. In all, 32% of the men discontinued the therapy <2 months after RAP and were deemed noncompliant with an additional 39% discontinuing therapy by 6 months, with the high cost of medication being the primary reason (65%). Long‐term compliance and preoperative erectile dysfunction were independent predictors of potency return after adjusting for age and nerve sparing.

CONCLUSIONS

The high cost of medication remains a significant barrier to maintaining therapy. Noncompliance to PDE5I therapy in a tertiary care centre was much higher than reported in clinical trial settings. With longer‐term follow‐up, we need to further define the factors that improve overall recovery of sexual function after RAP.     

三维骨建模在全膝关节置换术中韧带平衡的作用

目的探讨以三维骨建模为基础、无需影像的计算机辅助系统在人工全膝关节置换术(totalknee arthroplasty,TKA)中韧带平衡的作用。方法2002年11月～2003年6月,采用后稳定型人工全膝关节,在Ceravision无需影像资料的三维骨建模系统导航监控下,辅助完成TKA21例。男5例,女16例,年龄64～79岁,平均72.4岁。其中2例既往行胫骨近端截骨术,1例行股骨远端截骨术。14例膝内翻,7例膝外翻。术前下肢全长X线正位片测量,内翻13°～外翻13°,平均2.36°;膝关节X线正位片测量,应力下内翻平均8.47°(内翻2°～内翻20°),应力下外翻平均3.63°(内翻7°～外翻12°)。结果术中导航系统测量,额面内翻12°～外翻10°,平均3.33°,与术前比较差异有统计学意义(P<0.05);额面应力下内翻平均6.47°(内翻0°～内翻24°),应力下外翻平均4.32°(内翻8°～外翻15°),与术前比较差异有统计学意义(P<0.05)。术毕导航系统测得膝内外翻平均0.175°(内翻2°～外翻3°),而术后下肢全长X线正位片测量平均0.3°(内翻3.5°～外翻1.5°),二者差异无统计学意义(P>0.05)。术后3个月关节活动度为105～130°,平均115°,膝关节额面松弛度0.2～0.5cm,平均0.27cm。人工膝关节胫、股骨假体取得满意的对位置入和韧带平衡,无关节失稳和髌骨脱位等并发症发生。结论以三维骨建模为基础、无需影像的Ceravision系统,具有三维立体定位、优化截骨,并通过旋转对位和韧带松解获得伸屈膝关节等距间隙与韧带平衡稳定的作用,近期临床疗效满意,可在TKA中常规使用。     

Mid-term outcomes of rapid deployment aortic prostheses in patients with small aortic annulus

 Open in a separate windowOBJECTIVESThe Edwards Intuity valve is a rapid deployment aortic prosthesis that favours less invasive approaches. However, evidence about the clinical behaviour of their smaller sizes is scarce. Herein, we studied haemodynamic behaviours and clinical outcomes of small Intuity prostheses (19–21 mm) in comparison to larger Intuity prostheses (>21 mm).METHODSThis is an observational study including patients implanted with an Edwards Intuity rapid deployment aortic prosthesis. Patients with prosthesis sizes 19–21 and >21 mm were included. Baseline and perioperative variables, as well as adverse events during the follow-up were recorded and compared between groups.RESULTSA total of 122 patients (37% female, mean age 75 ± 4.5 years) were included, of whom 54 (45%) were implanted with a small prosthesis and 68 (55%) with a prosthesis >21 mm. There were no significant differences between patients with small Intuity prostheses and patients with larger prostheses regarding in-hospital mortality (2% vs 4%, P = 0.43) or mortality during the follow-up (3.41 vs 2.45 per 100 patients-years; P = 0.58). Survival in the small Intuity valve group was 95% at 1 year and 83% at 6 years, whereas in the larger Intuity valve group was 96% at 1 year and 78% at 6 years. The presence of a small prosthesis did not influence mid-term survival (log-rank P-value = 0.62).CONCLUSIONSThis study showed good clinical performance of Intuity aortic prostheses with appropriate mid-term survival in patients with the small aortic annulus. Thus, the Edwards Intuity rapid deployment aortic prosthesis may be considered as a potential option in patients with the small aortic annulus.