Adjustable buttons for ACL graft cortical fixation partially fail with cyclic loading and unloading.

PURPOSE: Despite good initial pullout strength, it is unclear whether adjustable button (AB) devices for anterior cruciate ligament (ACL) soft-tissue graft fixation, which are based on the Chinese finger trap technique, resist cyclic loading. Furthermore, they have never been tested in a cyclic protocol including complete unloading. It was hypothesized, that the displacement of AB devices with the Chinese finger trap technique would be greater than that of continuous suture loop devices and other available AB mechanisms in a cyclic loading with complete unloading protocol. METHODS: ACL reconstruction was performed in a porcine knee model using three different types of cortical fixation devices: two different AB devices that use the Chinese finger trap design, one AB device that uses a locked suture loop mechanism and two different continuous loop devices as control groups (n = 40). Specimens were mounted in a material-testing machine (Instron Inc.) that permitted 2500 loading and complete unloading cycles to a maximum of 250 N, as well as continuous elongation recording. A one-way ANOVA was performed for statistical analysis. RESULTS: The displacement of ABs with a Chinese finger trap loop (mean 8.1; SD 1.5 mm and mean 6.1; SD 1.4 mm) was significantly greater than that of AB with a locked suture loop (mean 4.7; SD 1.0 mm; p < 0.05) and devices with a continuous loop (mean 4.1; SD 0.5 mm and mean 4.4, SD 0.3 mm; p < 0.01). No significant differences were detected between the ABs with a locked suture loop and the continuous loops. CONCLUSION: Cyclic loading and unloading of AB using the Chinese finger trap technique leads to significantly greater construct lengthening compared with other devices. Complete unloading of the ACL is very likely to occur during rehabilitation after ACL reconstruction. Lengthening of the AB device due to cyclic loading might be a potential mode of failure of the ACL graft fixation. Therefore, when using an AB femoral fixation technique, a locked suture loop design or a careful rehabilitation protocol should be considered.

[Operative treatment in orthopedics and trauma surgery : Are more operations carried out in Germany?] / Operative Versorgung in Orthopädie und Unfallchirurgie : Wird in Deutschland immer mehr operiert?

BACKGROUND: Since 2005, when the Diagnosis-Related Group (DRG) system was introduced, an increasing number of surgical procedures have been reported in Germany. In particular, the numbers of elective arthroplasty and spinal surgery procedures have been controversial. OBJECTIVES: The focus of this study was analyzing the development of spinal surgery, arthroplasty, and fracture management. MATERIALS AND METHODS: We analyzed the database for all musculoskeletal operating procedure codes (OPS codes 5­78 to 5­86) from 2005 to 2013 collected by the German Federal Statistical Office. RESULTS: With an increase in total patient numbers of 12.8%, there was a rise in in-patient musculoskeletal procedures of 43.5%; the highest increase in procedures was found in spinal surgery (130%). Despite an ageing population, the numbers of hip- and knee arthroplasty procedures initially decreased after 2011 and after 2009 respectively. The number of osteosyntheses showed a slight increase (16%), whereas the number of (elective) implant removals declined (-7%). An increase in novel techniques was noticeable, such as locked plate osteosynthesis (251%), shoulder arthroplasty (402%) or the use of bone substitutes in spinal surgery (+2,011%). CONCLUSIONS: Despite generally increasing volume growth, the numbers of hip and knee arthroplasty cases decreased. In addition to an ageing population and potential economic incentives, technical innovations and new implant systems should be considered when discussing increasing case numbers.

Converting round tendons to flat tendon constructs: Does the preparation process have an influence on the structural properties?

PURPOSE: The structural properties of hamstring tendon grafts were evaluated in a porcine model, after processing it to a flat shape, to better replace or augment anatomic flat structures (e.g. ACL, MPFL or MCL). METHODS: In this biomechanical study, porcine flexor tendons were used which have a comparable shape to semitendinosus and gracilis tendons. One part of the tendon was prepared to a flat tendon construct by splitting the tendon longitudinally with a knife to half of the diameter of the tendon. The semi-split tendon was scratched out to a flat shape. The other matched part was tested in its original round shape. The tendons (n = 40) have been fixed in a uniaxial testing machine (Zwick/Roell) by cryo-clamps after preparing the fixed ends by 2-0 polyester sutures (2-0 Ethibond® EXCEL, Ethicon, Somerville, NJ). In every specimen, there was a free 60-mm tendon part between both clamps. The tendons have been loaded to failure to evaluate typical biomechanical parameters such as stiffness, yield load and maximum load. RESULTS: No statistically significant differences (n.s.) regarding stiffness, yield load and maximum load between natively round and processed flat tendons could be detected. CONCLUSION: A prepared flat-shaped tendon does not show any different structural properties compared with an original round tendon. Therefore, a flat tendon seems to be a biomechanical stable graft option for anatomic reconstruction or augmentation of injured natively flat-shaped structures such as MCL, MPFL or ACL.

Evaluation of biomechanical properties: are porcine flexor tendons and bovine extensor tendons eligible surrogates for human tendons in in vitro studies?

INTRODUCTION: Porcine flexor tendons, bovine extensor tendons, and human (semitendinosus) tendons are frequently used as substitutes for human ACL grafts in biomechanical in vitro studies. This study compares the biomechanical properties and structural differences of these tendons. MATERIALS AND METHODS: In this biomechanical study, fresh-frozen porcine flexor tendons, bovine extensor tendons, and human semitendinosus tendons were used (n = 36). The tendons were mounted in a uniaxial testing machine (Zwick/Roell) with cryo-clamps, leaving a 60 mm tendon part free between the two clamps. Specimens have been loaded to failure to evaluate the biomechanical parameters stiffness, yield load, and maximum load. A Total Collagen Assay Kit was used to detect differences in the total collagen type I concentration (n = 30). A one-way ANOVA was performed to detect differences in the means. The significance level was set at p < 0.05. RESULTS: There were no significant differences in the stiffness between the groups (bovine 194 ± 43 N/mm, porcine 211 ± 63 N/mm, and human cadaveric 208 ± 58 N/mm). The yield and maximum loads were high (>1000 N) in all groups, but they were significantly increased in both animal specimens (means of 1681-1795 N) compared with human cadaveric specimen (means of 1289-1406 N; p < 0.01). No difference in the collagen type I concentration was detected (N.S.). CONCLUSION: Porcine flexor and bovine extensor tendons are eligible substitutes with similar stiffness and high failure loads compared with human cadaveric semitendinosus tendons in in vitro studies.

A lateral fracture step-off of 2mm increases intra-articular pressure following tibial plateau fracture.

INTRODUCTION: The aim of this study was to evaluate the effects of increasing posttraumatic step-offs after lateral tibial plateau fracture reduction on the intra-articular pressure. MATERIALS AND METHODS: In eight fresh-frozen human cadaveric knees with intact menisci, a standardized sagittal osteotomy of the lateral tibial condyle was performed as an OTA/AO type 41-B1 fracture-model. The fragment was fixed by a customized sled including an angular stable tibia plate to evaluate step-offs from 0 mm to 8 mm in 1mm increments. In a servo-hydraulic testing machine, an axial force was applied to the tibial plateau in 0° (700N), 15° (700N), 30° (700N), 60° (350N), and 90 ° (350N) of flexion while the joint pressure was recorded by two pressure sensors. RESULTS: A 1mm step-off did not result in an increased joint pressure. At 60° of flexion a 2mm step-off increased the lateral joint pressure by 61.84kPa (P = 0.0027). In 30° of flexion, a 3mm step raised the lateral joint pressure by 66.80kPa (p = 0.0017), whereas in 0°, 15° and 90° of flexion, a 4mm step increased the pressure by >50kPa (P < 0.05). Concomitant medial joint pressure increments were lower than those in the lateral plateau. A significant increase of 19-24kPa in the medial joint pressure was detected in 90° of flexion with a 1mm lateral step (P = 0.0075), in 15° and 60° of flexion with a 2mm step (P < 0.05), in 0° of flexion with a 4mm step (P = 0.0215) and in 30° of flexion with a 7mm step (P = 0.0487). CONCLUSION: Lateral fracture step-offs of 2mm or larger should be reduced intraoperatively to avoid large increases in lateral joint pressure.

[Arthroscopic treatment of tibial plateau fractures]. / Arthroskopisch gestützte Versorgung der Tibiakopffraktur.

OBJECTIVE: The aim of arthroscopically assisted treatment of tibial plateau fractures is to achieve minimally invasive reduction and internal fixation of the joint fracture of the tibial plateau. Using the arthroscopic procedure, both the approach morbidity and the control of the articular reduction can be optimized. INDICATIONS: Displaced tibia plateau fractures of AO type A1 and B1/2/3 or Tscherne P2. CONTRAINDICATIONS: Strongly displaced tibial plateau fractures, which require an open surgical approach and stabilization with plate fixation (e.g., AO type C fractures or Moore type 5 fractures); 2nd and 3rd degree open fractures. Danger of compartment syndrome. SURGICAL TECHNIQUE: Planning of the surgical approach and confirmation of the indication by CT imaging. Diagnostic arthroscopy of the knee joint with treatment of associated injuries and confirming the indications for arthroscopically assisted reduction. Under arthroscopic control, insertion of an ACL tibial aiming device. In the central portion of the dislocated fracture fragment, a 2.4 mm K-wire is placed with the help of the aiming device. Opening of the outer cortex using a cannulated drill (9-11 mm diameter), introduction of a cannulated plunger below the fracture resulting in reduction of the fracture and compression of the cancellous bone below the fracture. Simultaneously the reduction is controlled by arthroscopy. Finally, the fracture is fixed using minimally invasive screw fixation (3.5-7.3 mm cancellous screws with washers) or by plate osteosynthesis (e.g., support plate). The metaphyseal defect can optionally be filled with bone substitute material. POSTOPERATIVE MANAGEMENT: Rehabilitation is dependent on the extent of the fracture. In arthroscopically treated fractures, partial weight bearing of 20 kg over a period of 6-12 weeks is usually necessary.