OBJECTIVE:To analyze the potential of the dual outer diameter screw and systematically evaluate the pull-out force of the dual outer diameter screw compared to the uncemented and cemented standard pedicle screws with special regard to the pedicle diameter and the vertebra level.METHODS:Sixty vertebrae of five human spines (T 6 -L 5 ) were sorted into three study groups for pairwise comparison of the uncemented dual outer diameter screw, the uncemented standard screw, and the cemented standard screw, and randomized with respect to bone mineral density (BMD) and vertebra level. The vertebrae were instrumented, insertion torque was determined, and pull-out testing was performed using a material testing machine. Failure load was evaluated in pairwise comparison within each study group. The screw-to-pedicle diameter ratio was determined and the uncemented dual outer diameter and standard screws were compared for different ratios as well as vertebra levels.RESULTS:Significantly increased pull-out forces were measured for the cemented standard screw compared to the uncemented standard screw (+689 N, P < 0.001) and the dual outer diameter screw (+403 N, P < 0.001). Comparing the dual outer diameter screw to the uncemented standard screw in the total study group, a distinct but not significant increase was measured (+149 N, P = 0.114). Further analysis of these two screws, however, revealed a significant increase of pull-out force for the dual outer diameter screw in the lumbar region (+247 N, P = 0.040), as well as for a screw-to-pedicle diameter ratio between 0.6 and 1 (+ 488 N, P = 0.028).CONCLUSIONS:For clinical application, cement augmentation remains the gold standard for increasing screw stability. According to our results, the use of a dual outer diameter screw is an interesting option to increase screw stability in the lumbar region without cement augmentation. For the thoracic region, however, the screw-to-pedicle diameter should be checked and attention should be paid to screw cut out, if the dual outer diameter screw is considered.

In total knee arthroplasty (TKA), patellofemoral groove design varies greatly and likely has a distinct influence on patellofemoral biomechanics. To analyse the selective influence, five patellofemoral design variations were developed based on Genesis II total knee endoprosthesis (original design, being completely flat, being laterally elevated, being medially elevated, and both sides elevated) and made from polyamide using rapid prototyping. Muscle-loaded knee flexion was simulated on 10 human knee specimens using a custom-made knee simulator, measuring the patellofemoral pressure distribution and tibiofemoral and patellofemoral kinematics. The measurements were carried out in the native knee as well as after TKA with the 5 design prototypes. The overall influence of the different designs on the patellofemoral kinematics was small, but we found detectable effects for mediolateral tilt (p<0.05 for 35°–80° flexion) and translation of the patella (p<0.045 for 20°–65° and 75°–90°), especially for the completely flat design. Considering patellofemoral pressures, major interindividual differences were seen between the designs, which, on average, largely cancelled each other out. These results suggest that the elevation of the lateral margin of the patellofemoral groove is essential for providing mediolateral guidance, but smooth contouring as with original Genesis II design seems to be sufficient. The pronounced interindividual differences identify a need for more patellofemoral design options in TKA.

Objectives Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). Materials and Methods A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res 2016;5:419–426.

ABSTRACT Objective: Infection after total hip (THA) and knee arthroplasty (TKA) is a serious complication which typically leads to a long lasting and intensive surgical and medicamentous treatment. The aim of this study was to identify factors that influence outcome after revision surgery caused by prosthetic infection. Methods: We retrospectively analyzed 64 patients who had revision surgery between 1989 and 2009 due to periprosthetic infection. We examined a total of 69 joints (TKA: 36%, THA: 64%), follow-up 5.1 years (0.5-21 years) after the initial surgical intervention. The mean patient age at time of surgery was 67 years old (43-79 years old). Clinical data and scores including the Western Ontario and McMaster Universities (WOMAC)-Index, the Harris Hip Score (HHS) and the Hospital for Special Surgery Score (HSS) were surveyed. Results: There was no difference in clinical scores regarding treatment between a single and a multiple stage treatment regime. Infections with multiple microorganisms and Enterococcus spp. lead to a significantly higher number of interventions. Using a modified Tsukayama system we classified 24% as type I, 34% type II and 42% type III- infections, with no differences in clinical outcome. Overweight patients had a significantly lower HHS and WOMAC-score. Immunosuppression leads to a worse WOMAC and HSS-Score. An increased number of procedures was associated to a limping gait. Conclusion: Thorough surgical technique leads to good clinical results independent of infection-type and treatment philosophy. Level of Evidence III, Case Control Study.

Background: Anterior cruciate ligament rupture can lead to symptomatic instability, especially during pivoting activities, which are often associated with increased anterior and rotational tibial loading. Therefore, the purpose of our robot-aided in-vitro study was to analyze the influence of tibial rotation on anterior knee stability under three anterior cruciate ligament conditions.Methods: Ten human knee specimens were examined using a robotic system. Anterior tibial translations were measured during anterior force application at internally and externally rotated positions of the tibia (5 steps until 4 Nm was reached) at 20 degrees, 60 degrees, and 90 degrees of flexion. The native knee was compared with the knee with deficient and replaced anterior cruciate ligamentFindings: Tibial rotation significantly influenced anterior tibial translation (P < 0.001), with differences of up to 12 mm between the largest and smallest anterior translation in the deficient knee. The largest influence of the anterior cruciate ligament on anterior translation was found in slightly externally rotated positions of the tibia (5 degrees-10 degrees at 20 degrees of flexion; 0 degrees-5 degrees at 90 degrees of flexion). Significantly increased anterior tibial translation (up to 7 mm) was measured after anterior cruciate ligament resection, which could be almost completely restored by the replacement (remaining difference < 1 mm) over a wide range of tibial rotations.Interpretation: Tibial rotation clearly influences anterior tibial translation. Because the greatest effect of the anterior cruciate ligament was found in slightly externally rotated positions of the tibia, increased attention to tibial rotation should be paid when performing the Lachman and anterior drawer tests. (C) 2015 Elsevier Ltd. All rights reserved.

Anterior Cruciate Ligament (ACL) rupture is one of the most common sport injuries [1]. While the importance of the cruciate ligaments for stabilization of the knee in anteroposterior (AP) direction is evident, their influence on rotational knee stability is still discussed controversially, especially since the doublebundle technique for ACL replacement claims the advantage of improved rotational stability [2,3]. Patients after ACL rupture often report symptomatic knee instability and giving way, especially during fast cutting and pivoting activities. During these activities, enhanced internal and external rotations occur in addition to anterior and posterior loading of the knee. Therefore, the aim of the current study was to systematically analyze the influence of tibial rotation on AP stability of the knee, comparing different conditions of the cruciate ligaments.

BACKGROUND AND OBJECTIVES: Despite the recommendations of national and international societies for the treatment of patients with acute neck and back pain, still too many radiologic examinations were performed. The purpose of this study was to analyze and optimize diagnostics and treatment of patients with acute back pain.METHODS: The medical records of 484 patients presented to the emergency clinic with acute neck or back pain were analyzed for clinical history, physical examination, radiographic findings and therapy.RESULTS: Radiographs of the lumbar, cervical, or thoracic spine were performed in 338 cases (70%). Radiographs were normal in 142 patients (42%) and degenerative changes were identified in 123 patients (36%). Only 2 patients (0.4%) had radiographic findings that had direct therapeutic relevance: 1 patient with metastatic disease and 1 patient with posttraumatic C1-C2 instability. For most patients without sensorimotor deficits and absent specific indications for radiography ("red flags"), therapy was not affected by the results of radiography.CONCLUSIONS: Plain radiography of the spine was unnecessary in most patients initially evaluated with non-specific acute back pain and does not improve the clinical outcome. The implementation of national and international guidelines is a slow process, but helps to reduce costs and to protect patients from unnecessary ionizing radiation exposure.

Considering the discrepant results of the recent biomechanical studies, the purpose of this study was to simulate dynamic muscle-loaded knee flexion with a large number of specimens and to analyse the influence of total knee arthroplasty (TKA) without and with patellar resurfacing on the patellofemoral pressure distribution.

Although mid- to long-term results after total ankle replacement have improved because of available second- and third-generation devices, failure of total ankle replacement is still more common compared with total hip replacement and total knee replacement . The portfolio of available total ankle replacement revision component options is small. Furthermore, the bone stock of the tibiotalar region is scarce making it difficult and in some situations impossible to perform revision total ankle replacement. In these cases tibiotalar and tibiotalocalcaneal fusions are valuable options. This article describes which surgical procedures should be performed depending on the initial situation and gives detailed advice on surgical technique, postoperative care, and clinical results.

OBJECTIVE The aim of this study was to analyze the setting for dislocations and redislocations after primary and revision total hip arthroplasty (THA), identify risk factors and optimize treatment. METHODS This study included 56 patients with a dislocated hip following THA (n=5,205) between 1984 and 2005 and a matched control group (n=55). Hospital charts and radiographs of all patients in both groups were analyzed. Thirty-one patients in the study group were followed both clinically and radiologically. RESULTS The dislocation rate after primary THA was 1.1% (56/5,205) and the redislocation rate after a first occurrence was as high as 39%. There was a positive correlation between the time intervals from the surgery to first dislocation and from the first dislocation to second dislocation (r=0.4). Most of the primary dislocations occurred within a short period of time after surgery, thus favoring consecutive dislocations. Female gender, as well as revision arthroplasty, was associated with a higher incidence of dislocations. No relation was found between the orientation of the acetabular cup and dislocation. CONCLUSION To prevent redislocations after the first occurrence, we suggest thorough evaluation of possible technical faults which should be addressed surgically. Considering the high redislocation rate, we also advocate a stringent conservative treatment regime especially after the first THA dislocation.

Custom femoral components have been developed for total hip arthroplasty to maximize cortical form-fit and thereby to reduce the problems of stress shielding and aseptic loosening. Limited information is available about how much endosteal cortical contact can actually be achieved with these expensive implants. The aim of this study was therefore to verify the exact cortical contact of a custom made stem using microsections and comparing it to a standard stem with similar design. In 8 human femurs (3 matched pairs and 2 separate specimens), custom femoral prostheses (Adaptiva; 5 femurs: 3 matched and 2 separate) and conventional femoral prostheses (Alloclassic; 3 matched femurs) were implanted. Endosteal cortical contact was determined from CAD planning drafts and microsections cut from the specimens with a diamond saw. Microsection analysis of the paired femurs showed that contact between prosthesis and bone varied clearly along the length of the femoral stem. Total cortical contact was considerably greater in custom prostheses than conventional prostheses (custom, 47%; conventional, 32%), but markedly less than the total contact predicted by the manufacturer (84% to 90%). The custom prosthesis had more lateral cortical contact on CAD planning drafts (cortical contact: medial, 60%; lateral, 53%) than on specimen microsections after implantation (medial, 64%; lateral, 24%). In summary, the philosophy of anchorage of both prostheses types could be confirmed. However, areas of cortical contact of the custom made prosthesis were considerably smaller compared to the pre-operative planning.

Considerable immediate periprosthetic bone density changes after implantation of femoral stems have been observed comparing DEXA measurements taken pre- and post-operatively. This is important in relation to the interpretation of DEXA studies.We analysed these density changes under standardised experimental conditions. Five human femora were implanted with a custom made femoral stem and ten femora with a standard cementless prosthesis. Densitometry was performed at various stages of implantation.Following rasping only slight density changes were noted (-2.7% to +0.7%). Comparing post-implantation and pre-operative measurements, all custom made stems with a proximal press-fit demonstrated clear increases in proximal periprosthetic bone density of +11% and +14%. In contrast, the standard prosthesis with a distal press-fit showed a loss of -5% and -2% in the proximal zones. Measurements following removal of the implants demonstrated hardly any density changes (0% to -4%) compared to the pre-operative measurements.We concluded that compacting of trabecular bone or bone loss due to rasping are not the main causes of density changes. Substantial measuring errors exist. For examination of periprosthetic bone density changes, pre-operative initial measurements should not be used as a baseline for comparison. Studies should commence with an immediate postoperative measurement.

Patients with Fontan circulation represent a significant cardiorespiratory risk during spinal surgery. We report about two patients with severe scoliosis and Fontan circulation and their successful operative treatment. The case report will be compared with the national and international literature.

Background: In this retrospective study, both the patients' and surgeons' satisfaction with resection of the first through fifth metatarsal heads for long-standing rheumatoid forefoot deformity was evaluated. Methods: Thirty-four patients (56 feet) had first through fifth metatarsal head resection. After a mean time of 5.3 years, 39 feet (69.6%) (26 patients) were examined clinically and radiographically. Results: The complication rate was 14% (8 of 56). There were four superficial and four deep wound infections. Plantar pressure pain under the resected metatarsal heads occurred in six feet. Most patients rated their cosmetic and functional results as good. Eighteen percent of patients (6 of 34) were satisfied and 78% (26 of 34) were satisfied with reservations. Thirty-three percent of patients (11 of 34) were pain free and 53% (18 of 34) had mild pain. The surgeons assessment of the patients' anatomical correction (cosmesis) was good in 90% (50 of 56) and poor in 10% (6 of 56). Conclusions: Our results, which are comparable to those of other studies, confirm the success of metatarsal head resection for the treatment of inflammatory forefoot destruction in rheumatoid arthritis to correct deformity, reduce pain, improve ambulation, and offer the patient a greater variety of shoewear.