The learning curve of patient-specific unikondylar arthroplasty may be advantageous to off-the-shelf implants: A preliminary study.

INTRODUCTION: Introducing a new arthroplasty system into clinical routine is challenging and could have an effect on early results. Since UKA are known to have failure mechanisms related to technical factors, reliable results and easy adoption are ideal. The question remains whether there are differences in objective procedure parameters in the early learning curve of different UKA systems. METHODS: two different UKA implants (Biomet Oxford[BO] followed by Conformis iuni[CI]) were introduced consecutively into clinical routine. We retrospectively analyzed the first 20 cases of each implant for one arthroplasty surgeon regarding operating time, correction of the mechanical axis, learning curve parameters, and revision rate of implants for 1.5 years postoperatively. RESULTS: Operating time (BO:98.3 ± 26.3min, CI:83.85 ± 21.8min (p < 0.078)), and tourniquet time differed in favor of the CI implant (BO:97.5 ± 29.5min; CI:73.5 ± 33.2 min; p < 0.017)). Mechanical alignment was restored in boths (preop:BO:mean 2.9°varus, CI:2.7°varus, postop:BOmean1.3°varus, CI:1°varus), while one BO patient and two CI patients were overcorrected. Operating time decreased from the first five implants to implants 16-20 for CI (95.2 ± 18.5min to 69 ± 21.5min, p < 0.076) and BO (130.6 ± 27.6min to 78 ± 17.3min, p < 0.009). Within 18 months of follow-up, 2 BO and 1 CI implants were revised. CONCLUSION: The introduction of an UKA implant was associated with longer surgery in both implants. Procedure time seems to differ between implants, while a learning curve was observed regarding instrumentation. CI implants seem to be reliable and adaptable in a medium-volume practice. The early results of this retrospective single-surgeon study were in favor of the individualized implant. Certainly, further studies encompassing larger cohorts with various implants are needed.

[Atraumatic fractures of the spine : Current strategies for diagnosis and treatment]. / Atraumatische Frakturen der Wirbelsäule : Aktuelle Strategien zur Diagnose und Therapie.

Atraumatic fractures of the spine are a common orthopedic disease condition that can be asymptomatic or associated with complaints of varying intensity and quality. The risk factors for such fracture forms are often metabolic and genetic diseases, which have a direct or indirect effect on bone metabolism and therefore secondarily affect the stability of the spinal vertebrae. Furthermore, benign and malignant tumors as well as infectious diseases can also be causative for atraumatic spinal fractures; however, those factors that are attributable to lifestyle habits should also not be underestimated. The treatment of affected patients is complex and nearly always interdisciplinary. In addition to purely symptom-oriented treatment concepts, orthoses in particular and when indicated surgical treatment procedures can be implemented. This article summarizes the important clinical, diagnostic and therapeutic aspects of atraumatic spinal fractures.

[Cell-based and future therapeutic strategies for femoral head necrosis]. / Zellbasierte und zukünftige Therapieansätze der Femurkopfnekrose.

BACKGROUND: The application of cell- and growth factor-based techniques in conjunction with conventional surgical approaches has great therapeutic potential for the treatment of avascular necrosis of the femoral head (AVNFH). OBJECTIVES: This review provides an overview of new strategies for the treatment of AVNFH, with emphasis on cell and growth factor-based approaches. MATERIALS AND METHODS: The results of a literature search are summarised, the most relevant publications are presented and discussed by the authors. RESULTS: In the focus of new strategies for treatment of AVNFH are bone marrow-derived cell concentrates and ex vivo-expanded mesenchymal stem cells. Besides local application during core decompression, the systemic administration of cells via blood vessels supplying the femoral head is an interesting approach. The application of osteogenic and angiogenic growth factor-laden scaffold materials has also been clinically tested. Initial results of randomised clinical trials using cell- and growth factor-based approaches underline the potential of these innovative therapeutic strategies. Cell-based therapies are governed by EU law and generally require a manufacturing authorization. CONCLUSION: To date, only few randomized controlled clinical trials are available which additionally display a considerable diversity concerning cell parameters, cell processing, adjuvant surgical techniques and the quality outcome parameters. Therefore, a final statement about the effectiveness of new cell and growth factor-based strategies is currently not possible.

[Endoprosthetic wear analysis using virtual CAD-based radiographs]. / Abriebanalyse mit virtuellen CAD-basierten Röntgenaufnahmen in der Endoprothetik.

The articulating parts of an endoprosthetic joint are subjected to constant wear, which results in loss of material. In peri-implant tissue, the wear debris particles cause aseptic inflammation with osteolysis and aseptic loosening. Due to the associated bone resorption-which can be considerable-"particle disease" represents a significant challenge for orthopedic surgeons. Continuous improvements in the material properties of polyethylene during the past decades have resulted in reduced wear and longer implant survival times. To evaluate wear properties in polyethylene liners after total hip arthroplasty in vivo, different graphics-based, semiautomatic software packages were developed to measure femoral head penetration in radiographic image series. However, the reduced wear properties of the new materials rendered their precise analysis and evaluation more difficult, and no software was able to reproduce the accuracy of the complex and expensive radiostereometric analysis first described by Selvik in 1974, which is still viewed as the gold standard. The aim of this study is to describe the validation of a novel and accurate method to analyze polyethylene wear in vivo using virtual computer-aided detection/diagnosis (CAD)-based radiographic images. Furthermore, its use is presented based on the first 5­year follow-up results of a multicenter approach evaluating the impact of vitamin E-blended polyethylene in cementless total hip replacement. Our data support the high accuracy of CAD-based virtual evaluation.

Experimental and computational studies on the femoral fracture risk for advanced core decompression.

BACKGROUND: Two questions are often addressed by orthopedists relating to core decompression procedure: 1) Is the core decompression procedure associated with a considerable lack of structural support of the bone? and 2) Is there an optimal region for the surgical entrance point for which the fracture risk would be lowest? As bioresorbable bone substitutes become more and more common and core decompression has been described in combination with them, the current study takes this into account. METHODS: Finite element model of a femur treated by core decompression with bone substitute was simulated and analyzed. In-vitro compression testing of femora was used to confirm finite element results. FINDINGS: The results showed that for core decompression with standard drilling in combination with artificial bone substitute refilling, daily activities (normal walking and walking downstairs) are not risky for femoral fracture. The femoral fracture risk increased successively when the entrance point is located further distal. The critical value of the deviation of the entrance point to a more distal part is about 20mm. INTERPRETATION: The study findings demonstrate that optimal entrance point should locate on the proximal subtrochanteric region in order to reduce the subtrochanteric fracture risk. Furthermore the consistent results of finite element and in-vitro testing imply that the simulations are sufficient.

The distribution of nociceptive innervation in the painful hip: a histological investigation.

Our understanding of the origin of hip pain in degenerative disorders of the hip, including primary osteoarthritis, avascular necrosis and femoroacetabular impingement (FAI), is limited. We undertook a histological investigation of the nociceptive innervation of the acetabular labrum, ligamentum teres and capsule of the hip, in order to prove pain- and proprioceptive-associated marker expression. These structures were isolated from 57 patients who had undergone elective hip surgery (44 labral samples, 33 ligamentum teres specimens, 34 capsular samples; in 19 patients all three structures were harvested). A total of 15,000 histological sections were prepared that were investigated immunohistochemically for the presence of protein S-100, 68 kDa neurofilament, neuropeptide Y, nociceptin and substance P. The tissues were evaluated in six representative areas. Within the labrum, pain-associated free nerve ending expression was located predominantly at its base, decreasing in the periphery. In contrast, the distribution within the ligamentum teres showed a high local concentration in the centre. The hip capsule had an almost homogeneous marker expression in all investigated areas. This study showed characteristic distribution profiles of nociceptive and pain-related nerve fibres, which may help in understanding the origin of hip pain.