The Effect of Taper Angle and Spline Geometry on the Initial Stability of Tapered, Splined Modular Titanium Stems.

Design parameters affecting initial mechanical stability of tapered, splined modular titanium stems (TSMTSs) are not well understood. Furthermore, there is considerable variability in contemporary designs. We asked if spline geometry and stem taper angle could be optimized in TSMTS to improve mechanical stability to resist axial subsidence and increase torsional stability. Initial stability was quantified with stems of varied taper angle and spline geometry implanted in a foam model replicating 2cm diaphyseal engagement. Increased taper angle and a broad spline geometry exhibited significantly greater axial stability (+21%-269%) than other design combinations. Neither taper angle nor spline geometry significantly altered initial torsional stability.

Cadaveric results of an accelerometer based, extramedullary navigation system for the tibial resection in total knee arthroplasty.

INTRODUCTION: In total knee arthroplasty, the accuracy and precision of the tibial resection must be improved. The purpose of this study was to determine the accuracy and time associated with the use of an accelerometer based, extramedullary surgical navigation system for performing the tibial resection. MATERIALS AND METHODS: Four orthopedic surgeons performed a tibial resection utilizing the KneeAlign™ system, each on five separate, cadaveric tibiae. Each surgeon was assigned a preoperative "target" of varus/valgus alignment and posterior slope prior to each resection. The alignment of each resection was measured using both plain radiographs and computed tomography, along with the time required to use the device. RESULTS: Regarding coronal alignment, the mean absolute difference between the preoperative "target" and tibial resection alignment was 0.77° ± 0.64° using plain radiograph, and 0.68° ± 0.46° using CT scan measurements. Regarding the posterior slope, the mean absolute difference between the preoperative "target" and the tibial resection was 1.06° ± 0.59° using plain radiograph, and 0.70° ± 0.47° using CT scan measurements. The time to use the KneeAlign™ for the fifth specimen was less than 300 s for all four orthopedic surgeons in this study. DISCUSSION: This cadaveric study demonstrates that the KneeAlign™ system is able to accurately align the tibial resection in both the coronal and sagittal planes.

Early outcome of a modular femoral component in revision total hip arthroplasty.

Forty-six hips in 42 patients underwent revision surgery with a modular femoral component (ZMR; Zimmer, Warsaw, Ind). Thirty-nine hips with 2 to 5 years' follow-up were evaluated radiographically and clinically by the Harris hip score and WOMAC pain/stiffness/function scores. The Harris hip score improved from 47.4 to 72.3 (P<.001), with significant improvements in the WOMAC pain/stiffness/function scores. The mean subsidence was 4.4 mm, with 5 hips demonstrating significant subsidence of more than 5 mm. Four hips required reoperation, 1 due to failure of the femoral component. No early complications were encountered regarding the modular junction. Modular, cementless, extensively porous, coated femoral components have demonstrated early clinical and radiographic success. Distal intramedullary fit helps ensure initial stability; proximal modularity further maximizes fit while optimizing hip offset and length.

The accuracy of subacromial corticosteroid injections: a comparison of multiple methods.

Corticosteroids are commonly used in the treatment of the impingement syndrome. Efficacy, as well as accurate placement, have been questioned. The purpose of this prospective, randomized study is to assess the accuracy of subacromial injections and to correlate accuracy with short term clinical outcome at 3 months. Sixty shoulders, which were diagnosed with impingement syndrome, were randomized to receive a subacromial injection of corticosteroids, local anesthetic, and contrast dye from 1 of 3 locations: anterolateral, lateral, or posterior. Accuracy was confirmed by 3 radiographic views of the shoulder, while clinical ratings were assessed by the UCLA shoulder score and a 10-point visual pain analog scale during the initial, post-injection, and 3-month visits. The overall accuracy was 70%, with no difference among the 3 portals. Accuracy was not related to body mass index. Furthermore, accurate injections did not significantly improve the UCLA score, pain scale, or patient satisfaction at 3 months. In contrast, accurate injections produced a positive Neer's impingement test more often (35/39 vs 9/16; P = .009). Overall, there was an improvement in the UCLA score (26.2-32.2; P < .001) and a decrease in the pain scale (7.2-3.43; P < .001) at 3-month follow-up. In conclusion, the accuracy of injection was 70%. Clinical improvement did not correlate with accuracy; however, accuracy did reliably produce a positive impingement test. This multimodal treatment plan did produce significant improvement in shoulder function and pain level in the short term.

A comparison of the results of total hip and knee arthroplasty performed on a teaching service or a private practice service.

BACKGROUND: Active participation of residents and fellows in the performance of total hip and total knee arthroplasties may affect the outcomes of these procedures. We evaluated the early clinical results and complications associated with primary total hip and knee arthroplasties at a hospital that had both university teaching and private practice orthopaedic services. METHODS: We performed a retrospective study on a consecutive series of 347 patients who had undergone 230 total hip and 171 total knee procedures performed by one attending surgeon. One hundred and sixty-nine patients underwent an arthroplasty during which a resident or fellow on a teaching service assisted the attending surgeon; during these procedures, the resident or fellow performed part of the arthroplasty under the direct supervision of the attending surgeon. Subsequently, 178 patients underwent an arthroplasty performed by the same surgeon without resident or fellow participation. RESULTS: Significantly longer operative times were recorded for both total hip arthroplasty (average, seventy-three compared with sixty-one minutes; p < 0.0001) and total knee arthroplasty (average, eighty compared with seventy-three minutes; p = 0.0028) when the procedures were performed with the participation of residents or fellows. For total hip arthroplasty the complication rates were 8% for the teaching service and 10% for the private practice service, and for total knee arthroplasty they were 3% for each service. With the numbers studied, there were no differences in any clinical outcomes between the groups. CONCLUSIONS: Teaching and active participation from residents and fellows during total hip and total knee arthroplasty did not have a detrimental effect on the early clinical results, except for a longer surgical time.