Klaus Michael Stürmer

Influence of platelet-rich plasma on chondrogenic differentiation and proliferation of chondrocytes and mesenchymal stem cells.

Background/Aims: Autologous chondrocyte (CC) transplantation has the disadvantages of requiring two surgical interventions and in vitro expansion of cells, implying the risk of cellular dedifferentiation. Our clinical aim is to develop a one-step procedure for autologous CC transplantation, i.e. harvesting, isolation and reimplantation of CC performed in one single surgical procedure. Platelet-rich plasma (PRP) is a source of autologous growth factors reported to have mitogenic effects. The objective of this study was to test the influence of PRP as an autologous scaffold on freshly isolated CC and mesenchymal stem cells (MSC). Methods: CC and MSC were subjected to two- or three-dimensional (3D) growth systems, either with or without PRP. Chondrogenic differentiation was determined via quantification of collagen type II mRNA and immunohistochemical staining. Results: We observed a proliferative effect for MSCs exposed to PRP in monolayer culture and an increase in the expression of chondrogenic markers when cells are exposed to a 3D environment. CCs exposed to PRP show a decrease in the chondrogenic phenotype with increasing proliferative activity. Conclusion: PRP has a proliferative effect on CCs and MSCs. In a one-step procedure for autologous CC transplantation, this might be an advantage over other scaffold materials, but confirmation in in vivo studies is required.

Anatomy of Lateral Patellar Instability: Trochlear Dysplasia and Tibial Tubercle–Trochlear Groove Distance Is More Pronounced in Women Who Dislocate the Patella

Background A trend toward young women being at greatest risk for primary and recurrent dislocation of the patella is evident in the current literature. However, a causative factor is missing, and differences in the anatomical risk factors between men and women are less defined. Purpose To identify differences between the sexes in the anatomy of lateral patellar instability. Study Design Case control study; Level of evidence, 3. Methods Knee magnetic resonance images were collected from 100 patients treated for lateral patellar instability. Images were obtained from 157 patients without patellar instability who served as controls. Using 2-way analyses of variance, the influence of patellar dislocation, gender, and their interaction were analyzed with regard to sulcus angle, trochlear depth, trochlear asymmetry, patellar height, and the tibial tubercle—trochlear groove (TT-TG) distance. Mechanisms of injury of first-time dislocations were divided into high-risk, low-risk, and no-risk pivoting activities and direct hits. Results For all response variables, a significant effect was observed for the incidence of patellar dislocation (all P < .01). In addition, sulcus angle, trochlear asymmetry, and trochlear depth depended significantly on gender (all P < .01) but patellar height did not (P = .13). A significant interaction between patellar dislocation and gender was observed for the TT-TG distance (P = .02). The mean difference in TT-TG distance between study and control groups was 4.1 mm for women (P < .01) and 1.6 mm for men (P = .05). Low-risk and no-risk pivoting injuries were most common in women, whereas first-time dislocations in men occurred mostly during high-risk pivoting activities (P < .01). Conclusion The data from this study indicate that trochlear dysplasia and the TT-TG distance is more prominent in women who dislocate the patella. Both factors might contribute to an increased risk of lateral patellar instability in the female patient as illustrated by the fact that dislocations occurred most often during low-risk or no-risk pivoting activities in women.

Value of the tibial tuberosity-trochlear groove distance in patellar instability in the young athlete.

Background A lateralized tibial tubercle may be a relevant anatomic factor in patients with patellar instability and can be used as an indication for a distal realignment procedure. However, parameter values for the tibial tuberosity–trochlear groove (TT-TG) distance in the young patient have not been defined. It also remains to be determined how this parameter contributes to patellar instability in the growing knee joint. Purpose The purpose of this study was to evaluate the value of the TT-TG distance in patellar instability in the young athlete. Study Design Case control study; Level of evidence, 3. Methods Knee magnetic resonance images were collected from 109 patients with lateral patellar instability and from 136 control subjects. Student t test and multiple logistic regression analysis were used to compare the absolute and relative values of the TT-TG distance between patients and controls. The relative value was defined as the ratio between the TT-TG distance and the total width of the distal femur. Results The TT-TG distance (absolute and relative to femur width) differed significantly between patients with patellar dislocation and the control group (both P < .01). The TT-TG distances were on average 4 mm larger in patients with patellar dislocation; TT-TG distance divided by femur width was on average 5% larger in patients with patellar dislocation. Multiple logistic regression analysis confirmed the TT-TG distance as a significant risk factor for patellar dislocation (P = .04), but showed no significant interaction with patient age or femur width (P = .95 and P = .15, respectively). Conclusion A lateralized tibial tubercle is a relevant anatomic factor in the young athlete and in the adult patient with lateral patel-lar instability. Its parameter values and its influence on patellar dislocation are independent of patient age and should therefore be evaluated as in adults.

Magnetic resonance imaging characteristics of the medial patellofemoral ligament lesion in acute lateral patellar dislocations considering trochlear dysplasia, patella alta, and tibial tuberosity-trochlear groove distance.

PURPOSE The objective of this study was to analyze the injury patterns of the medial patellofemoral ligament (MPFL) in acute lateral patellar dislocations (LPDs) considering the anatomically relevant factors of patellar instability. METHODS Knee magnetic resonance images were collected from 73 patients within 7 weeks after LPD, and the injury patterns of the MPFL were evaluated for trochlear dysplasia, for patellar height, and for the tibial tuberosity-trochlear groove (TT-TG) distance. RESULTS Injury to the MPFL was found in 98.6% of the patients (72 of 73) after the acute LPD, with a complete tear in 51.4% (37 of 72), most frequently localized at the femoral attachment site, and a partial tear in 48.6% (35 of 72). Injury to the femoral origin (Fem), to the midsubstance (Mid), and to the patellar insertion (Pat) of the MPFL was found in 50.0% (36 of 72), 13.9% (10 of 72), and 13.9% (10 of 72), respectively. More than 1 site of injury was found in 22.2% (16 of 72), most frequently as a combined injury at the femoral origin and at the patellar insertion sites (Pat+Fem) (13 of 16). The study population, as well as the Pat, Fem, and Pat+Fem subgroups, showed significantly different values of trochlear dysplasia and patellar height when compared with the control group, whereas the data of the Mid group were not significantly different. In addition, injury at the patellar insertion (Pat) was accompanied by a significantly increased TT-TG distance when compared not only with the control group but also with the Fem, Mid, and Pat+Fem groups. CONCLUSIONS The data from our study indicate that patterns of MPFL injury depend on trochlear dysplasia, patellar height, and TT-TG distance. They show a new aspect in the complex interplay between active, passive, and static stabilizers of the patellofemoral joint. LEVEL OF EVIDENCE Level IV, diagnostic case-control study.

Standardized Bending and Breaking Test for the Normal and Osteoporotic Metaphyseal Tibias of the Rat: Effect of Estradiol, Testosterone, and Raloxifene

The fracture of bone plays a key role in osteoporosis. BMD measurement, however, is only an indirect parameter of this phenomenon. We therefore developed a highly sensitive three‐point bending test for the metaphyseal tibias in rats to evaluate stiffness and strength. This was validated in a right‐left comparison and a bioassay with soy‐free food, estradiol, raloxifene, and testosterone in orchidectomized rats.

A New Posterolateral Approach Without Fibula Osteotomy for the Treatment of Tibial Plateau Fractures

The selection of a surgical approach for the treatment of tibia plateau fractures is an important decision. Approximately 7% of all tibia plateau fractures affect the posterolateral corner. Displaced posterolateral tibia plateau fractures require anatomic articular reduction and buttress plate fixation on the posterior aspect. These aims are difficult to reach through a lateral or anterolateral approach. The standard posterolateral approach with fibula osteotomy and release of the posterolateral corner is a traumatic procedure, which includes the risk of fragment denudation. Isolated posterior approaches do not allow sufficient visual control of fracture reduction, especially if the fracture is complex. Therefore, the aim of this work was to present a surgical approach for posterolateral tibial plateau fractures that both protects the soft tissue and allows for good visual control of fracture reduction. The approach involves a lateral arthrotomy for visualizing the joint surface and a posterolateral approach for the fracture reduction and plate fixation, which are both achieved through one posterolateral skin incision. Using this approach, we achieved reduction of the articular surface and stable fixation in six of seven patients at the final follow-up visit. No complications and no loss of reduction were observed. Additionally, the new posterolateral approach permits direct visual exposure and facilitates the application of a buttress plate. Our approach does not require fibular osteotomy, and fragments of the posterolateral corner do not have to be detached from the soft tissue network.

Patellar dislocations in children, adolescents and adults: A comparative MRI study of medial patellofemoral ligament injury patterns and trochlear groove anatomy

PURPOSE The first aim was to compare medial patellofemoral ligament injury patterns in children and adolescents after first-time lateral patellar dislocations with the injury patterns in adults. The second aim was to evaluate the trochlear groove anatomy at different developmental stages of the growing knee joint. MATERIALS AND METHODS Knee magnetic resonance (MR) images were collected from 22 patients after first-time patellar dislocations. The patients were aged 14.2 years (a range of 11-15 years). The injury pattern of the medial patellofemoral ligament was analysed, and trochlear dysplasia was evaluated with regard to sulcus angle, trochlear depth and trochlear asymmetry. The control data consisted of MR images from 21 adult patients who were treated for first-time lateral patellar dislocation. RESULTS After patellar dislocation, injury to the medial patellofemoral ligament was found in 90.2% of the children and in 100% of the adult patients. Injury patterns of the medial patellofemoral ligament were similar between the study group and the control group with regard to injury at the patellar attachment site (Type I), to the midsubstance (Type II) and to injury at the femoral origin (Type III) (all p>0.05). Combined lesions (Type IV) were significantly less frequently observed in adults when compared to the study group (p=0.02). The magnitude of trochlear dysplasia was similar in children, adolescents and adults with regard to all three of the measured parameter-values (all p>0.05). In addition, the articular cartilage had a significant effect on the distal femur geometry in both paediatrics and adults. CONCLUSION First, the data from our study indicated that the paediatric medial patellofemoral ligament injury patterns, as seen on MR images, were similar to those in adults. Second, the trochlear groove anatomy and the magnitude of trochlear dysplasia, respectively, did not differ between adults and paediatrics with patellar instability. Thus, physicians are confronted with similar anatomical risk factors and similar injuries to the medial soft-tissue restraints in children when compared to adults with patellar instability.

Metallic Biomaterials in Skeletal Repair

Metallic biomaterials are becoming increasingly important in skeletal repair. The goal of this review article is to present an overview of metallic implant materials currently used in trauma and orthopedic surgery. Further, new research trends and future clinical concepts are described and discussed. Titanium, titanium alloys, stainless steels and CoCr alloys are used as bone implants in orthopedic and trauma surgery. Especially titanium and its alloys currently constitute the most highly favoured implant materials for joint replacement and osteosynthesis. In comparison to other metallic implant materials, titanium is characterized by a high biocompatibility, a good workability and corrosion resistance with suitable mechanical properties (low Young’s modulus—high strength). To improve orthopedic implants, there is a trend in current research towards the development of new titanium alloys with improved biological and biomechanical properties. To achieve a fast and safe bone fixation of the implants, optimized surface characteristics and surface structures are applied. Biomimetic coatings with and without the ability to release growth factors and cell coatings even including the development of stem-cell-coated titanium implants for the partial surface replacement of joints are under investigation.

Prognostic reliability of the Hawkins sign in fractures of the talus.

Objective: To determine the prognostic reliability, sensitivity, and specificity of the Hawkins sign. The Hawkins sign is a subchondral radiolucent band in the talar dome that is indicative of viability at 6 to 8 weeks after a talus fracture. It is visible in the anterior-posterior view, but seldom appears on lateral radiographs. Design: Retrospective study. Setting: University hospital. Patients and Methods: Between January 1995 and December 2000, a total of 41 patients (13 female, 28 male) with displaced talar fractures were operated on in our hospital. Thirty-four patients with a mean age of 35 years (range 12-60) were followed for more than 36 months (range 36-52). The prognostic reliability of the Hawkins sign was studied in 31 of these patients using a two-by-two table. The Ankle-Hindfoot scale of the American Orthopaedic Foot and Ankle Society (AOFAS) was used as an outcome measure. Results: No Hawkins sign was found in the five patients who developed avascular necrosis (AVN) of the talus. In the remaining 26 patients who did not develop AVN, a positive (full) Hawkins sign was observed 11 times, a partially positive Hawkins sign 4 times, and a negative Hawkins sign 11 times. The Hawkins sign thus showed a sensitivity of 100% and a specificity of 57.7%. The Hawkins sign (if present) appeared between the 6th and the 9th week after trauma. Mean [range] AOFAS scores were: Pain, 31 [10-40] out of 40; Function, 39 [14-50] out of 50; and Alignment, 7 [0-10] out of 10. The clinical results were satisfactory. Conclusion: The Hawkins sign is a good indicator of talus vascularity following fracture. If a full or partial positive Hawkins sign is detected, it is unlikely that AVN will develop at a later stage after injury.

Migration, Matrix Production and Lamellar Bone Formation of Human Osteoblast-Like Cells in Porous Titanium Implants

The goal of this study was to characterize growth, mineralization and bone formation of osteoblast-like cells in titanium pore channels of defined diameter. Titanium implants with continuous drill channels of diameters of 300, 400, 500, 600 and 1,000 µm were inserted into human osteoblast-like cell cultures. The ingrowth of the cells into the drill channels was investigated by transmitted-light microscopy and scanning electron microscopy. Immunofluorescence and histological analysis of 15-channel sections of each diameter were used to investigate the growth behavior and the matrix protein patterns. Mineralization was evidenced by Alizarin red staining and high-resolution microradiography. The ingrowth of human osteoblast-like cells in the drill channels occurred in a sequence of four characteristic stages. In stage 1, osteoblast precursor cells adhered to the wall of the channel and migrated three-dimensionally into the channel by forming foot-like protoplasmic processes. For all 15 sample drill channels that were investigated, the cell ingrowth over 20 days amounted on average to 793 µm (± 179) into 600-µm-diameter channels, where they migrated significantly faster than in all the other channels. In stage 2, approximately on day 5–7, the osteoblast-like cells began to anchor on the substrate wall by matrix proteins and to build up a dense network of matrix proteins in the drill channel. The mineralization of the extracellular matrix, while depending on cell stimulation, was initiated in stage 3, on average after 4 weeks. In drill channels of a diameter of 1,000 µm the cell growth was incomplete and no mineralization was found by radiological assessment. Starting in week 6, in the drill channels of diameters ranging from 300 to 600 µm, the network of extracellular matrix proteins and osteoblast-like cells began to form an osteon-like structure. Neither the highly developed migration behavior of osteoblastic cells nor the reorganization from a fiber-like matrix to a lamellar structure have so far been described for cell cultures.