Evaluation of 3 Fixation Devices for Tibial-Sided Anterior Cruciate Ligament Graft Backup Fixation.

We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for anterior cruciate ligament reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw (all Arthrex). Thirty skeletally mature porcine tibiae were used. The first group was prepared by graft fixation within the tibial tunnel using only an interference screw. The second and third groups included an interference screw with 2 types of secondary fixation: 4.5-mm bicortical post and SwiveLock anchor. Mechanical testing consisted of 500 cycles between 50 and 250 N at 1 Hz, followed by a pull to failure conducted at 20 mm per minute. Ultimate load-to-failure testing demonstrated the largest mean (SD) load tolerated in the post/washer group, 1148 (186) N, versus the SwiveLock group, 1007 (176) N, and the screw-only group, 778 (139) N. There was no statistical difference between the 2 backup fixation groups. Use of a SwiveLock anchor as backup fixation at the tibial side in soft-tissue anterior cruciate ligament reconstruction is a safe, effective alternative to a bicortical post and provides statistically equivalent pullout strength with unlikely requirement for future hardware removal.

Angle stable nails provide improved healing for a complex fracture model in the femur.

BACKGROUND: Conventional nails are being used for an expanding range of fractures from simple to more complex. Angle stable designs are a relatively new innovation; however, it is unknown if they will improve healing for complex fractures. QUESTIONS/PURPOSES: When comparing traditional and angle stable nails to treat complex open canine femur fractures, the current study addressed the following questions: do the two constructs differ in (1) radiographic evidence of bone union across the cortices; (2) stability as determined by toggle (torsional motion with little accompanying torque) and angular deformation; (3) biomechanical properties, including stiffness in bending, axial compression, and torsional loading, and construct failure properties in torsion; and (4) degree of bone tissue mineralization? METHODS: Ten hounds with a 1-cm femoral defect and periosteal stripping were treated with a reamed titanium angle stable or nonangle stable nail after the creation of a long soft tissue wound. Before the study, the animals were randomly assigned to receive one of the nails and to be evaluated with biomechanical testing or histology. After euthanasia at 16 weeks, all operative femora were assessed radiographically. Histological or biomechanical evaluation was conducted of the operative bones with nails left in situ compared with the nonoperative contralateral femora. RESULTS: Radiographic and gross inspection demonstrated hypertrophic nonunion in all 10 animals treated with the nonangle stable nail, whereas six of 10 animals treated with the angle stable nail bridged at least one cortex (p = 0.023). The angle stable nail construct demonstrated no toggle in nine of 10 animals, whereas all control femora exhibited toggle. The angle stable nail demonstrated less angular deformation and toggle (p ≤ 0.005) and increased compressive stiffness (p = 0.001) compared with the conventional nonangle stable nail. Histology demonstrated more nonmineralized tissue in the limbs treated with the conventional nail (p = 0.005). CONCLUSIONS: Angle stable nails that eliminate toggle lead to enhanced yet incomplete fracture healing in a complex canine fracture model. CLINICAL RELEVANCE: Care should be taken in tailoring the nail design features to the characteristics of the fracture and the patient.

A comparison of standard and high-flexion knees: are we getting what we expected?

Some patients have been less than satisfied with flexion after total knee arthroplasty (TKA). As early designs provided limited flexion, companies have developed high-flexion designs. We conducted a study to compare flexion between 2 standard and 3 high-flexion designs and to compare clinical and radiographic postoperative flexion. Clinical and radiographic measurements were obtained by 3 independent orthopedists. Clinical flexion, with the patient maximally bending his or her knee as far as possible, was measured with a goniometer, recorded, and compared with measurements from lateral radiographs of the knee in the same position. A total of 144 knees (108 patients) were included in the study. Mean preoperative flexion was 110° for both groups, and mean postoperative flexion was 111° clinically and 109° radiographically for the standard designs, and 114° clinically and 117° radiographically for the high-flexion designs (P<.05). The groups had similar preoperative and postoperative Knee Society knee and function scores. Measurements obtained by the 3 independent examiners were highly correlated. Compared with the standard designs, the highflexion designs demonstrated statistically significantly more flexion, though the clinical increase in flexion was relatively small (3º).

Measured flexion following total knee arthroplasty.

Postoperative flexion is an important factor in the outcome of total knee arthroplasty. Although normal activities of daily living require a minimum of 105° to 110° of flexion, patients from non-Western cultures often engage in activities such as kneeling and squatting that require higher flexion. The desire to achieve greater flexion serves as the driving force for prosthetic modifications, including high-flexion designs. Techniques used to measure knee flexion and knee position during measurement are not often described or are different depending on the examiner. The purpose of this study was to compare active (self) and passive (assisted) flexion after successful total knee arthroplasty for 5 prostheses (2 standard and 3 high-flexion) using clinical (goniometer) and radiographic (true lateral radiograph) measurement techniques by different independent examiners.At a mean follow-up of 2.7 years (range, 1-5.6 years), a total of 108 patients (144 total knee arthroplasties) had completed the study. Mean postoperative active flexion was 111° clinically and 109° radiographically for the standard designs and 114° clinically and 117° radiographically for the high-flexion designs. Adding passive flexion increased flexion to 115° clinically and 117° radiographically for the standard designs and 119° clinically and 124° radiographically for the high-flexion designs. Flexion differences between the 2 measurement techniques (active vs passive and clinically vs radiographically) were statistically significant (P<.05). These findings demonstrate the importance of describing how flexion is measured in studies and understanding how the method of measurement can affect the findings.

Cementless femoral fixation in total hip arthroplasty.

Cementless femoral fixation by means of bone ingrowth has been successful in total hip arthroplasty in patients with sufficient bone quality. Consistent bone ingrowth and resultant long-term success involve many factors, including surgical technique, initial mechanical stability achieved at time of implantation, stem design and material, and implant surface. One potential method for achieving faster, more consistent initial bone ingrowth is use of the osteoconductive ceramic hydroxyapatite. In addition, more stable initial fixation most likely improves long-term outcome. In this article, we review the criteria for successful cementless femoral fixation and the long-term results reported in the literature.