Suitability of Permanent Probe Implants For the Measurement of Intramedullary Perfusion and Temperature Near the Bone Cortex: A Pilot Study Using a Rabbit Model

This study was conducted to test the suitability of permanent probe implants for the measurement of  intramedullary perfusion by laser Doppler flowmetry and for the measurement of temperature near the  bone cortex. Measurements were carried out on the conscious animal in order to rule out the influence of  anaesthesia on intramedullary perfusion and temperature. During the first experimental animal trials, some  of the probes made of polysulphon broke and/or gave false temperature measurements, so the original  probe design was modified. The probes were reinforced with metal, and the temperature sensors were made  less permeable to moisture. These modified probes were found to be suitable for permanent measurement  of intramedullary perfusion and of temperature near the cortex in the conscious rabbit.

Process optimized minimally invasive total hip replacement

The purpose of this study was to analyse a new concept of using the the minimally invasive direct anterior approach (DAA) in total hip replacement (THR) in combination with the leg positioner (Rotex- Table) and a modified retractor system (Condor). We evaluated retrospectively the first 100 primary THR operated with the new concept between 2009 and 2010, regarding operation data, radiological and clinical outcome (HOOS). All surgeries were perfomed in a standardized operation technique including navigation. The average age of the patients was 68 years (37 to 92 years), with a mean BMI of 26.5 (17 to 43). The mean time of surgery was 80 min. (55 to 130 min). The blood loss showed an average of 511.5 mL (200 to 1000 mL). No intra-operative complications occurred. The postoperative complication rate was 6%. The HOOS increased from 43 points pre-operatively to 90 (max 100 points) 3 months after surgery. The radiological analysis showed an average cup inclination of 43° and a leg length discrepancy in a range of +/− 5 mm in 99%. The presented technique led to excellent clinic results, showed low complication rates and allowed correct implant positions although manpower was saved

Repetitive recombinant human bone morphogenetic protein 2 injections improve the callus microarchitecture and mechanical stiffness in a sheep model of distraction osteogenesis

Evidence suggests that recombinant human bone morphogenetic protein 2 (rhBMP-2) increases the mechanical integrity of callus tissue during bone healing. This effect may be either explained by an increase of callus formation or a modification of the trabecular microarchitecture. Therefore the purpose of the study was to evaluate the potential benefit of rhBMP-2 on the trabecular microarchitecture and on multidirectional callus stiffness. Further we asked, whether microarchitecture changes correlate with optimized callus stiffness. In this study a tibial distraction osteogenesis (DO) model in 12 sheep was used to determine, whether percutaneous injection of rhBMP-2 into the distraction zone influences the microarchitecture of the bone regenerate. After a latency period of 4 days, the tibiae were distracted at a rate of 1.25 mm/day over a period of 20 days, resulting in total lengthening of 25 mm. The operated limbs were randomly assigned to one treatment groups and one control group: (A) triple injection of rhBMP-2 (4 mg rhBMP-2/injection) and (B) no injection. The tibiae were harvested after 74 days and scanned by µCT (90 µm/voxel). In addition, we conducted a multidirectional mechanical testing of the tibiae by using a material testing system to assess the multidirectional strength. The distraction zones were tested for torsional stiffness and bending stiffness antero-posterior (AP) and medio-lateral (ML) direction, compression strength and maximum axial torsion. Statistical analysis was performed using multivariate analysis of variance (ANOVA) followed by student's t-test and Regression analysis using power functions with a significance level of P<0.05. Triple injections of rhBMP-2 induced significant changes in the trabecular architecture of the regenerate compared with the control: increased trabecular number (Tb.N.) (treatment group 1.73 mm/1 vs. control group 1.2 mm/1), increased cortical bone volume fraction (BV/TV) (treatment group 0.68 vs. control group 0.47), and decreased trabecular separation (Tb.Sp.) (treatment group 0.18 mm vs. control group 0.43 mm)

Clinical results of the Metha short hip stem: a perspective for younger patients?

In recent years, various uncemented proximal metaphyseal hip stems were introduced for younger patients as a bone preserving strategy. Initial osteodensitometric analyses of the surrounding bone of short stems indicate an increase of bone mass with secondary bone ingrowth fixation as a predictor of long-term survival of these types of implants. We report the outcome of 151 modular Metha short hip stem implants in 148 patients between March 2005 and October 2007. The mean follow-up was 5.8±0.7 years and the mean age of the patients was 55.7±9.8 years. Along with demographic data and co-morbidities, the Harris Hip Score (HHS), the Hip dysfunction and Osteoarthritis Outcome Score (HOOS), and also the results of a patient-administered questionnaire were recorded pre-operatively and at follow-up. The mean HHS increased from 46±17 pre-operatively to 90±5 the HOOS improved from 55±16 pre-operatively to 89±10 at the final follow-up. A total of three patients have been revised, two for subsidence with femoral revision and one for infection without femoral revision (Kaplan Meier survival estimate 98%). The radiological findings showed no radiolucent lines in any of the patients. The modular Metha short hip stem was implanted in younger patients, who reported an overall high level of satisfaction. The clinical and radiographic results give support to the principle of using short stems with metaphyseal anchorage. However, long-term results are necessary to confirm the success of this concept in the years to come

ERRATUM: Repetitive recombinant human bone morphogenetic protein 2 injections improve the callus microarchitecture and mechanical stiffness in a sheep model of distraction osteogenesis

Due to a technical error, Dr. Marc-Frederic Pastor was omitted from the author list of this article. The correct author details appear above.<br /

In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution

Background: In recent years magnesium alloys have been intensively investigated as potential resorbable materials with appropriate mechanical and corrosion properties. Particularly in orthopedic research magnesium is interesting because of its mechanical properties close to those of natural bone, the prevention of both stress shielding and removal of the implant after surgery. Methods: ZEK100 plates were examined in this in vitro study with Hank's Balanced Salt Solution under physiological conditions with a constant laminar flow rate. After 14, 28 and 42 days of immersion the ZEK100 plates were mechanically tested via four point bending test. The surfaces of the immersed specimens were characterized by SEM, EDX and XRD. Results: The four point bending test displayed an increased bending strength after 6 weeks immersion compared to the 2 week group and 4 week group. The characterization of the surface revealed the presence of high amounts of O, P and Ca on the surface and small Mg content. This indicates the precipitation of calcium phosphates with low solubility on the surface of the ZEK100 plates. Conclusions: The results of the present in vitro study indicate that ZEK100 is a potential candidate for degradable orthopedic implants. Further investigations are needed to examine the degradation behavior

The effect of functional splinting on mild dysplastic hips after walking onset

BACKGROUND: For treatment of Graf class IIb dysplastic hips at walking onset a treatment concept with abduction splints allowing patterns as walking and crawling under constant abduction control was investigated. However, as the splint still incapacitates child movements the research question remains whether the physiologically progressing maturation of hips can be significantly altered using such abduction splints for walking children. METHODS: Of 106 children showing late hip dysplasia, 68 children treated with the Hoffman-Daimler (HD-splint) abduction splint were compared with 38 children with neglect of the abduction treatment in this retrospective study. Radiographic analyses were performed measuring the development of the age dependent acetabular angle. RESULTS: The regression analysis for splint treatment showed a significant linear regression for both splint treatment and no splint treatment group (r(2 )= 0,31 respectively r(2 )= 0,33). No statistical difference between both treatment groups was apparent. CONCLUSION: Considering the characteristics of this study, there seems to be no strong rationale supporting the use of an abduction device in growing children. As no significant difference between treatment groups is apparent, a future controlled prospective study on splinting effects can be considered ethically allowed

The clinical outcome of the different HemiCAP and UniCAP knee implants: A systematic and comprehensive review

The focal metallic cartilage resurfacing is a surgical method that offers an appropriate step between the biological techniques and arthroplasty in middle-aged patients with full-thickness cartilage defects. The advantages of this technique are that it addresses the defect, respects healthy tissues and provides stability and contoured surface similar to a full arthroplasty. A systematic review was conducted according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Two reviewers (MM and DC) independently conducted the search using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews (CDSR). These databases were searched for the terms hemicap knee implant and unicap knee implant and knee focal metallic implant. From the initial 21 studies that were evaluated, 10 were eligible for analysis. Considering both the HemiCAP focal implant and the HemiCap® Wave patellofemoral prosthesis, we found a lack of mid- to long-term clinical outcomes in well-designed prospective clinical studies. No Level I or II studies were found, while the limited number of patients who were included undermines the overall clinical results of these studies. The progression of osteoarthritis, the persisting pain and the subsequent high revision or failure rates in the limited available studies with long-term follow-up, seem to be the major drawbacks of these partial resurfacing techniques. Utilization of partial resurfacing for femoral or patellofemoral compartments results in good short-term outcome for middle-aged patients as a step between biological technique and total knee arthroplasty. The surgeon should be cognizant and also notify the patient of the high failure rates that are reported in the literature in mid- to longterm follow-up and ultimately, the decision to perform partial resurfacing should be taken by both the patient and the orthopedic surgeon

Simultaneous bilateral minimally invasive total hip arthroplasty: A comprehensive review of the literature

Several studies have reported that minimally- invasive total hip arthroplasty (MISTHA) may significantly reduce postoperative pain and results in faster postoperative rehabilitation when compared with the traditional lateral or posterior approach. Regarding bilateral hip osteoarthritis, there is still no consensus whether simultaneous bilateral MIS-THA can be established as the treatment of choice. Therefore, we searched the international databases of Pubmed, Medline, and Cochrane Database of Systematic Reviews using the key words minimally invasive bilateral total hip arthroplasty. From the initial 23 articles we found five clinical studies which met our inclusion criteria. From the perspective of possible intra- and postoperative complications, one-stage bilateral MIS THA was equally safe or safer than two-stage interventions. In addition, from a clinical outcome perspective, the one-stage procedure can be considered to be preferable. Higher blood transfusion requirements, which were expected following the standard bilateral simultaneous THA, seemed to be minimized with the simultaneous bilateral MIS THA. The supine position of the patient minimized the mean operation time. Approaches using the lateral decubitus position of the patient should be avoided in simultaneous bilateral THA due to the increased operation time. There is a lack of randomized, controlled clinical trials, comparing simultaneous bilateral MIS THA with staged bilateral MIS THA. Although simultaneous bilateral MIS THA seems to be efficacious, cost-effective and safe, more clinical trials are required to establish its superiority over the sequential MIS THA