Changes in femoral rollback and rotation with increasing coupling in knee arthroplasty-a biomechanical in-vitro study.

BACKGROUND: After total knee arthroplasty, 10-30% of patients still complain about knee pain, even after exact positioning of the components. Altered knee kinematics are crucial in this regard. The aim of our study was to experimentally determine the influence of different degrees of component coupling of knee prostheses on joint kinematics during muscle-loaded knee flexion in-vitro. METHODS: Femoral rollback and femoral rotation of a standard cruciate retaining (GCR), a posterior stabilized (GPS), a rotational hinge (RSL) and a total hinge (SSL) design of the same series of knee replacement implants (SL-series) of one single manufacturer (Waldemar Link GmbH, Hamburg, Germany) were analyzed and set in relation to the motion of the corresponding native knee in a paired study design. All different coupling degrees were analyzed in the same human knees. To simulate muscle loaded knee flexion, a knee simulator was used. Kinematics were measured with an ultrasonic motion capture system and integrated in a calculated coordinate system via CT-imaging. RESULTS: The largest posterior motion on the lateral side was found for the native knee (8.7 ± 7.0 mm), followed by the GPS (3.2 ± 5.1 mm) and GCR (2.8 ± 7.3 mm) implants, while no motion was found for the RSL (0.1 ± 3.0 mm) and the SSL (-0.6 ± 2.7 mm) implants. In contrast, on the medial side, only the native knee showed a posterior motion (2.1 ± 3.2 mm). Regarding femoral external rotation, the only implant where the observed difference did not reach statistical significance when compared to the native knee was the GCR (p = 0.007). CONCLUSION: The GCR and GPS kinematics closely imitate those of the native joint. Medial femoral rollback is reduced, however, with the joint pivoting around a rotational center located in the medial plateau. Without additional rotational forces, the coupled RSL and SSL prostheses closely resemble each other with no femoral rollback or relevant rotational component. The femoral axis, however, shifts ventrally in both models when compared with their primary counterparts. The positioning of the coupling mechanism in the femoral and tibial component thus can already lead to altered joint kinematics even in prostheses with an identical surface geometry.

Robot-aided in vitro measurement of patellar stability with consideration to the influence of muscle loading.

BACKGROUND: Anterior knee pain is often associated with patellar maltracking and instability. However, objective measurement of patellar stability under clinical and experimental conditions is difficult, and muscular activity influences the results. In the present study, a new experimental setting for in vitro measurement of patellar stability was developed and the mediolateral force-displacement behavior of the native knee analyzed with special emphasis on patellar tilt and muscle loading. METHODS: In the new experimental setup, two established testing methods were combined: an upright knee simulator for positioning and loading of the knee specimens, and an industry robot for mediolateral patellar displacement. A minimally invasive coupling and force control mechanism enabled unconstrained motion of the patella as well as measurement of patellar motion in all six degrees of freedom via an external ultrasonic motion-tracking system. Lateral and medial patellar displacement were measured on seven fresh-frozen human knee specimens in six flexion angles with varying muscle force levels, muscle force distributions, and displacement forces. RESULTS: Substantial repeatability was achieved for patellar shift (ICC(3,1) = 0.67) and tilt (ICC(3,1) = 0.75). Patellar lateral and medial shift decreased slightly with increasing flexion angle. Additional measurement of patellar tilt provided interesting insights into the different displacement mechanisms in lateral and medial directions. For lateral displacement, the patella tilted in the same (lateral) direction, and tilted in the opposite direction (again laterally) for medial displacement. With regard to asymmetric muscle loading, a significant influence (p < 0.03, up to 5 mm shift and 8° tilt) was found for lateral displacement and a reasonable relationship between muscle and patellar force, whereas no effect was visible in the medial direction. CONCLUSION: The developed experimental setup delivered reproducible results and was found to be an excellent testing method for the in vitro analysis of patellar stability and future investigation of surgical techniques for patellar stabilization and total knee arthroplasty. We demonstrated a significant influence of asymmetric quadriceps loading on patellar stability. In particular, increased force application on the vastus lateralis muscle led to a clear increase of lateral patellar displacement.

Practicability for robot-aided measurement of knee stability in-vivo.

BACKGROUND: For the analysis of different treatments concerning anterior cruciate ligament (ACL) rupture, objective methods for the quantification of knee stability are needed. Therefore, a new method for in-vivo stability measurement using a robotic testing system should be developed and evaluated. METHODS: A new experimental setting was developed using a KUKA robot and a custom-made chair for the positioning and fixation of the participants. The tibia was connected to the robot via a Vacoped shoe and magnetic buttons, providing adequate safety. Anterior tibial translation and internal tibial rotation were measured on both legs of 40 healthy human subjects at 30°, 60° and 90° of flexion, applying anterior forces of 80 N and internal torques of 4 Nm, respectively. RESULTS: While the mean differences between the right and left leg measured for anterior tibial translation were within an acceptable range (<1.5 mm), the absolute values were substantially large (38-40.5 mm). For mean internal tibial rotation, between 17.5 and 20° were measured at the different sides and flexion angles, with a maximal difference of 0.75°. High reproducibility of the measurements could be demonstrated for both, anterior tibial translation (ICC(3,1) = 0.97) and internal tibial rotation (ICC(3,1) = 0.94). CONCLUSIONS: Excellent results were achieved for internal tibial rotation, almost reproducing current in-vitro studies, but too large anterior tibial translation was measured due to soft-tissue compression. Therefore, high potential for the analysis of ACL related treatments concerning rotational stability is seen for the proposed method, but further optimization is necessary to enhance this method for the reliable measurement of anterior tibial translation.

Increased patellofemoral pressure after TKA: an in vitro study.

PURPOSE: 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. METHODS: In 22 cadaver knee specimens, dynamic muscle-loaded knee flexion (15°-90°) was simulated with a specially developed knee simulator applying variable muscle forces on the quadriceps muscles to maintain a constant ankle force. Patellofemoral pressures were measured with flexible, pressure-sensitive sensor foils (TEKSCAN) and patellofemoral offset with an ultrasound motion-tracking system (ZEBRIS). Measurements were taken on the native knee, after total knee arthroplasty and after patellar resurfacing. Correct positioning of the patellar implant was examined radiologically. RESULTS: The maximal patellofemoral peak pressure partly increased from the native knee to the knee with TKA with intact patella (35°-90°, p < 0.012) and highly increased (twofold to threefold) after patellar resurfacing (20°-90°, p < 0.001). Concurrently, the patellofemoral contact area decreased and changed from a wide area distribution in the native knee, to a punctate area after TKA with intact patella and a line-shaped area after patellar resurfacing. Patellar resurfacing led to no increase in patellar thickness and patellofemoral offset. CONCLUSIONS: Despite correct implantation of the patellar implants and largely unchanged patellofemoral offset, a highly significant increase in pressure after patellar resurfacing was measured. Therefore, from a biomechanical point of view, the preservation of the native patella seems reasonable if there is no higher grade patellar cartilage damage.

The effect of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral contact pressure during simulated partial weight-bearing knee flexion.

PURPOSE: The purpose of this in vitro study was to investigate the influence of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral pressure. METHODS: A dynamic muscle-loaded knee squat was simulated on eight knee specimens with an upright knee simulator while measuring tibiofemoral joint kinematics and patellofemoral pressure distribution. The quadriceps muscle was attached to three actuators simulating the three main extensor muscles, and five different quadriceps loading patterns were tested. RESULTS: Tibial axial and varus-valgus-rotation are affected most while changing quadriceps loading patterns from lateral to medial. Higher internal tibial rotation is associated with higher medial muscle load compared to the symmetrical loading condition. Contact force, contact area and maximum peak pressure rise with increasing flexion angles. Accentuating the vastus lateralis muscle induces a significant reduction in patellofemoral contact force and a 30% diminished contact area at 90° of flexion. CONCLUSION: Strengthening the vastus medialis muscle leads to increased internal tibial rotation, thus optimizing patella tracking by lowering the Q-angle. In contrast, weakness of the vastus medialis muscle causes decreased tibial internal rotation and is associated with lower patellofemoral contact pressure and contact area. Vastus medialis exercise is advisable to improve patella tracking but may not be recommended in patients with disorders due to increased patellofemoral contact pressure.

Long-term results of the custom- made hip endoprostheses Evolution K® and Adaptiva®: A prospective cohort study.

The aim of our study is to evaluate clinical long-term results and determine changes in periprosthetic bone density of the custom-made hip prostheses Evolution-K ® and Adaptiva ® . Periprosthetic bone density were evaluated by means of DEXA (LunariDXA- Prodigy® bone densitometer) with a long-term follow-up of 16 (15-18) years (Evolution-K®) in 24 patients and 13 (13-15) years (Adaptiva®) in 41 patients. Evolution- K® had a survival rate of 92% and yielded 79/100 points in Harris Hip Score, a mediocre result. Adaptiva® had a survival rate of 99% and achieved a good score of 88/100 points. Bone density measurements demonstrated the greatest loss of bone density in the proximal regions of interest (ROI) for both prosthesis types (Evolution-K®: -25.8% ROI 1, -40.3% ROI 7; -8.3% ROI 2, -10.4% ROI 6; Adaptiva®: -29.8% ROI 7, -6.8% ROI 6, +14.3% ROI 3, +3.1% ROI 4). Adaptiva® yielded a good clinical result as compared to Evolution-K® with only average clinical results. Both prostheses clearly showed signs of "stress shielding". Here, the Adaptiva® achieved reduced bone density loss as compared to the Evolution-K®.

[Implantation technique for the CUT-type femoral neck endoprosthesis]. / Implantationstechnik der Schenkelhalsprothese Typ CUT beim Hüftgelenkersatz.

OBJECTIVE: Total hip replacement with maximum preservation of femoral neck. Restoration of pain-free joint function. INDICATIONS: Coxarthrosis, femoral head necrosis in younger patients with intact femoral neck. CONTRAINDICATIONS: Joint infection. Coxa valga (caput-collum-diaphysis [CCD] angle > 150 degrees ). Coxa vara (CCD angle < 110 degrees ). Body mass index > 30 (relative contraindication). Ongoing chemotherapy. Osteoporosis. SURGICAL TECHNIQUE: Transgluteal or anterolateral approach. Resection of two thirds of the femoral head. Implantation of uncemented acetabular component. Revitalization of the femoral neck with special rasps for the CUT prosthesis. Trial reduction with bone rasp and modular cone in place (10 degrees or 20 degrees angle). Uncemented stem implantation. RESULTS: From 2002 to 2006, 49 uncemented CUT prostheses were implanted in 36 patients. Average age was 45.1 years (20-60 years). Inpatient stay amounted to 10.8 days and operating time to 74 min. Average blood loss through drainage was 795 ml, an average of 297 ml transfused back. Transfusion was necessary in ten patients. There were no cases of postoperative infection, nerve lesion, or hip dislocation. Patients were examined preoperatively and followed up at 6 weeks and 1 year. Harris Hip Score improved from 46.1 points preoperatively to 81.6 points at 6 weeks and 95.7 points at 1 year. Average leg length discrepancy of 0.7 cm (minimum -0.8, maximum 2.2 cm) was determined radiologically in 31 of 49 patients. It became necessary to replace two of the 49 stems due to aseptic loosening, in the first case at 19 months (femoral head osteonecrosis, lupus erythematosus, and taking cortisone), and in the second case 3 years after implantation (steroid-induced femoral head necrosis related to Crohn's disease and azathioprine [Imurek] therapy). One cone and head component had to be revised 1 month after implantation due to impingement syndrome. One ceramic head fractured 2.5 years after implantation so that cone and head required revision. The overall follow-up time was 37 months on average (minimum 12, maximum 55 months).

Influence of Different Patellofemoral Design Variations Based on Genesis II Total Knee Endoprosthesis on Patellofemoral Pressure and Kinematics.

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.

Pull out Strength of Dual Outer Diameter Pedicle Screws Compared to Uncemented and Cemented Standard Pedicle Screws: A Biomechanical in vitro Study.

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.

Long-term results after metatarsal head resection in the treatment of rheumatoid arthritis.

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.

CLINICAL OUTCOME AFTER INFECTED TOTAL KNEE AND TOTAL HIP ARTHROPLASTY.

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.

Tibial rotation influences anterior knee stability--a robot-aided in-vitro 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°, 60°, and 90° of flexion. The native knee was compared with the knee with deficient and replaced anterior cruciate ligament. FINDINGS: 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°-10° at 20° of flexion; 0°-5° at 90° 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<1mm) 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.

Spine radiography in the evaluation of back and neck pain in an orthopaedic emergency clinic.

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.

Changes in dissipated energy and contact pressure after osteochondral graft transplantation.

Osteochondral autologous transplantation is frequently used to repair small cartilage defects. Incongruence between the osteochondral graft surface and the adjacent cartilage leads to changed friction and contact pressure. The present study wanted to analyze the differences between intact and surgically treated cartilage surface in respect to contact pressure and frictional characteristic (dissipated energy). Six ovine carpometacarpal joints were used in the present study. Dissipated energy during instrumentally controlled joint movement as well as static contact pressure were measured in different cartilage states (intact, defect, deep-, flush-, high-implanted osteochondral graft and cartilage failure simulation on a high-implanted graft). The best contact area restoration was observed after the flush implantation. However, the dissipated energy measurements did not reveal an advantage of the flush implantation compared to the defect and deep-implanted graft states. The high-implanted graft was associated with a significant increase of the mean contact pressure and decrease of the contact area but the dissipated energy was on the level of intact cartilage in contrast to other treatments where the dissipated energy was significantly higher as in the intact state. However the cartilage failure simulation on the high-implanted graft showed the highest increase of the dissipated energy.

1.2 French stone retrieval baskets further enhance irrigation flow in flexible ureterorenoscopy.

Ureterorenoscopy (URS) has revolutionized upper urinary tract stone therapy. However, the size of the working channel and the stone baskets limit irrigation flow as well as vision. This study determined further improvements of irrigation flow, deflection capacities and impairments of breaking resistance in a new 1.2 French (F) ultra-miniaturized basket. Irrigation measurements were performed in semirigid URS (semiURS, working channel 5F) and in flexible URS (flexURS, 3.6F) in 0°, 90° and 270° deflection with 1.2F, 1.8F, 1.9F and 2.2F baskets and compared with empty channel. Breaking strength of 1.2F, 1.8F and 1.9F baskets were evaluated using a material testing machine. Tested baskets affected irrigation in semiURS and flexURS (p < 0.05). Mean ± SEM (standard error of the mean) for semiURS flow rates counted 197.1 ± 2.0, 140.9 ± 1.6, 111.1 ± 1.5, 98.0 ± 1.3 and 77.1 ± 0.9 ml/min for empty channel, 1.2F, 1.8F, 1.9F and 2.2F baskets (p < 0.05). Using unbent flexURS flow rates of 44.2 ± 0.4, 20.4 ± 0.2, 5.9 ± 0.1, 5.4 ± 0.1 and 1.5 ± 0.1 ml/min for empty channel, 1.2F, 1.8F, 1.9F and 2.2F baskets, were observed (p < 0.05). The 1.2F versus 2.2F basket showed a 13.6-fold increase in flexURS irrigation (p < 0.05), while only the 2.2F basket reduced deflection by 20.3 %. The breaking strength decreased with a reduced basket size (1.2F: 6.4 ± 0.46 vs. 1.8F: 16.8 ± 2.79 vs. 1.9F: 32.2 ± 2.74 N, p < 0.05). Ultra-miniaturized baskets of 1.2F ensured a sufficient irrigation flow as needed for high quality vision in URS stone management. However, miniaturization of the 1.2F basket resulted in a reduced breaking strength compared with larger sized devices which in turn may hamper stone removal by an increased vulnerability.

Dislocation after total hip arthroplasty: risk factors and treatment options.

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.

Proximal metatarsal osteotomy for hallux valgus: an audit of radiologic outcome after single screw fixation and full postoperative weightbearing.

BACKGROUND: Proximal metatarsal osteotomy combined with a distal soft-tissue procedure is a common treatment for moderate to severe hallux valgus. Secure stabilisation of the metatarsal osteotomy is necessary to avoid complications such as delayed union, nonunion or malunion as well as loss of correction. The aim of this study was to report our results using a single screw for stabilisation of the osteotomy. METHODS: We retrospectively reviewed 151 patients with severe hallux valgus who were treated by the above mentioned way with full postoperative weightbearing in a stiff soled shoe. Mean age of patients at time of surgery was 54 years, 19 patients were male and 132 female. Assessment of clinical and radiographic results was performed after 2 days and 6 weeks. Results were also correlated to the experience of the performing surgeon. RESULTS: Mean preoperative HVA (hallux valgus angle) was 36.4 degrees, and then 3.5 degrees 2 days and 13.4 degrees 6 weeks after the procedure (p < 0.001). Mean preoperative IMA (intermetarsal angle) was 16.8 degrees, and then 6.4 degrees after 2 days and 9.8 degrees after 6 weeks (p < 0.001). Mean preoperative first metatarsal length of 56.4 mm decreased to 53.6 mm after 6 weeks. Possible non-union of the osteotomy was observed in 4 patients (2.6%) after 6 weeks. Performing residents (n = 40) operated in 65 minutes and attending surgeons (n = 111) in 45 minutes, with no significant differences in radiographic measurements between both groups. CONCLUSIONS: Single screw stabilisation of proximal chevron osteotomy is a reliable method for treating severe hallux valgus deformities with satisfactory results.

Cytotoxic effect and tissue penetration of phenol for adjuvant treatment of giant cell tumours.

Local adjuvant treatment of giant cell tumours (GCTs) of the bone with phenol has led to a significant reduction in recurrence rates. In the current study, the optimal phenol concentration and duration of intralesional exposure were evaluated. Specimens of GCTs were exposed to various concentrations of phenol solution (6, 60 and 80%) for either 1 or 3 min. Following embedding in glutaraldehyde, the tumour cell layers were examined by transmission electron microscopy. Destroyed cell organelles indicated the penetration depth as a sign of denaturation. Incubation of GCT specimens with 6% phenol solution for 3 min resulted in the most tissue damage and the deepest tissue penetration of ∼200 µm. Incubation with 60 and 80% phenol solution reached a penetration depth of only ∼100 µm. Phenol instillation may be used for the treatment of small scattered cellular debris following intralesional curettage; however, it is not suitable for treatment of remaining solid tumour tissue of GCT. The use of high phenol concentrations has no benefit and increases the risk of local or systemic intoxication.

Dissipated energy as a method to characterize the cartilage damage in large animal joints: an in vitro testing model.

Several quantitative methods for the in vitro characterization of cartilage quality are available. However, only a few of these methods allow surgical cartilage manipulations and the subsequent analysis of the friction properties of complete joints. This study introduces an alternative approach to the characterization of the friction properties of entire joint surfaces using the dissipated energy during motion of the joint surfaces. Seven sheep wrist joints obtained post mortem were proximally and distally fixed to a material testing machine. With the exception of the carpometacarpal articulation surface, all joint articulations were fixed with 'Kirschner' wires. Three cartilage defects were simulated with a surgically introduced groove (16 mm(2), 32 mm(2), 300 mm(2)) and compared to intact cartilage without an artificial defect. The mean dissipated energy per cycle was calculated from the hysteresis curve during ten torsional motion cycles (±10°) under constant axial preload (100-900 N). A significant increase in dissipated energy was observed with increasing cartilage defect size and axial load (p<0.001). At lower load levels, the intact and 16 mm(2) defect showed a similar dissipated energy (p>0.073), while all other defect conditions were significantly different (p=0.015). All defect sizes were significantly different (p=0.049) at 900 N axial load. We conclude that the method introduced here could be an alternative for the study of cartilage damage, and further applications based on the principles of this method could be developed for the evaluation of different cartilage treatments.

Fusion following failed total ankle replacement.

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.