Stryker Howmedica Research Articles

A Biomechanical Comparison of Bosworth and Poly-L Lactic Acid Bioabsorbable Screws for Treatment of Acromioclavicular Separations

The purpose of this study was to determine the failure load of intact coracoclavicular ligaments and the pullout strength of a poly-L lactic acid screw (PLLA, Linvatec, Largo, FL) compared with a titanium screw (Bosworth, Stryker Howmedica Osteonics, Allendale, NJ) in the repair of fifth-degree acromioclavicular separations. Biomechanical cadaveric study. The ultimate tensile strength of coracoclavicular ligaments was determined using a servohydraulic testing machine (MTS, Eden Prairie, MN) by creating grade V acromioclavicular separations. Titanium Bosworth screws and Linvatec PLLA screws were placed across the reduced coracoclavicular joint and through the base of the coracoid process of right and left matched cadaveric shoulder specimens, respectively. The axial pullout strength was determined by MTS uniaxial tensile testing along the screw axis to determine the ultimate fixation failure load at a rate of 1 mm/second. Intact coracoclavicular ligaments required an axial load of 340.15 +/- 100.77 N to fail. The bioabsorbable PLLA screw provided fixation strength that was significantly less than the Bosworth screw fixation strength: 272.01 +/- 63.26 and 367.01 +/- 111.54 N, respectively (P < .05, paired t test). The titanium Bosworth screw restored strength to the acromioclavicular joint equivalent to the intact coracoclavicular ligament; however, the bioabsorbable PLLA screw fixation was significantly weaker than the intact ligaments and the Bosworth repair. Titanium Bosworth screws supply more strength of fixation in grade V acromioclavicular separations than the PLLA screw tested in this study.

A contemporary snapshot of the use of hydroxyapatite coating in orthopaedic surgery

The capacity for biological materials to combine with inorganic salts is well established. Bio-mineralisation was an evolutionary milestone, and a key contributor to the ‘cladogenesis of life’ which occurred in the early Cambrian period, 570 million years ago.[1][1] A protracted ice age in the

A simple precise technique for making the anterior cut in patellofemoral resurfacing

Patellofemoral resurfacing is becoming a popular option for the treatment of isolated patellofemoral damage. Rotational alignment of the trochlea in the coronal plane is important in ensuring optimum patellar tracking irrespective of whether a more anatomical trochlea such as in the FPV system (Wright Medical Arlington TN) or a symmetrical one such as in the Avon Patella (Stryker Howmedica Allendale NJ) is employed.

Comparison Between Triple-Tapered and Double-Tapered Cemented Femoral Stems in Total Hip Arthroplasty: A Prospective Study Comparing the C-Stem Versus the Exeter Universal Early Results After 5 Years of Clinical Experience

A prospective study was conducted comparing the early clinical and radiological results between the triple-tapered C-Stem (DePuy International, Leeds, UK) and the double-tapered Exeter Universal (Stryker Howmedica Osteonics, Mahwah, NJ) in cemented total hip arthroplasty. A total of 192 patients (200 hips) received the C-Stem and 189 patients (205 hips) received the Exeter Universal. Average follow-up was 29 and 31 months in the C-Stem and Exeter groups, respectively. From the short-term results, we found similar mean improvements in clinical scores and no difference was noted in the incidence of complications. Average subsidence was comparable (C-Stem, 0.77 mm ± 0.56; Exeter, 0.82 ± 0.63). Radiolucencies in the cement-stem and cement-bone interfaces were seen primarily in the proximal zones in both groups. No stems were considered at risk of aseptic loosening and the extent of proximal femoral resorption was comparable.

Clinical performance of a highly cross-linked polyethylene at two years in total hip arthroplasty: a randomized prospective trial

We report the 2-year results for a prospective randomized trial comparing highly cross-linked with standard polyethylene in total hip replacements. In our study, 46 hips were available for radiographic analysis at 2- and 3-year follow-up. Femoral bearings were 28-mm cobalt chrome with the polyethylene insert randomly selected at the time of implantation to be highly cross-linked polyethylene (Crossfire; Stryker Howmedica Osteonics, Allendale, NJ) or standard polyethylene (N 2/Vac, Stryker Howmedica Osteonics). Polyethylene wear rates were measured based on anterior-posterior (AP) and lateral pelvis radiographs at 6 weeks and at yearly intervals using a validated computer-assisted edge-detection method. Wear rates between the 2 groups were compared using the nonparametric Mann-Whitney test at the 95% level. A significant reduction in 2- and 3-dimensional linear wear rates (42% and 50%) was found in the highly cross-linked group ( P = .001 and P = .005).

Use of constrained acetabular components for hip instability: an average 10-year follow-up study

The short-term efficacy of using constrained acetabular components for hip instability in the total hip arthroplasty construct has been documented. However, long-term concerns including late dislocation, loosening of components, and osteolysis have not been addressed. The authors evaluated, at an average 10.3-year follow-up, 101 tripolar constrained components (Stryker Howmedica Osteonics) used in the total hip arthroplasty construct. At final follow-up, 6 hips had dislocated or had failure of the constrained component, 5 of which were revised. In addition, 4 hips were revised for aseptic loosening of the acetabular component, 4 hips were revised for aseptic femoral loosening, and 1 hip was revised for acetabular osteolysis. Considering the complexity of the cases, this component has provided durable fixation and hip stability at this intermediate-term follow-up.

Femoral impaction grafting in revision hip arthroplasty with irradiated bone

We evaluated the results of femoral impaction grafting with the Exeter stem (Stryker Howmedica Osteonics, Newbury, UK) and irradiated bone–graft. We followed 57 hips for an average of 27 months. Endo-Klinik grading showed 8 grade 1, 22 grade 2, and 27 grade 3 hips. Radiographic analysis revealed cortical repair in 34% and graft incorporation in 39% but no evidence of trabecular remodeling. Moderate subsidence (5–10 mm) occurred in 7 patients (12.5%), and massive subsidence (>10 mm) occurred in 4 patients (7%). Complications included 6 dislocations, 3 periprosthetic fractures, and 2 stem revisions. Impaction grafting with the Exeter system produces satisfactory results for most patients, but a few hips perform poorly, and the reasons for this are unclear. We have concerns about irradiated bone–graft because the characteristic changes of graft remodeling are not seen. Copyright 2002, Elsevier Science (USA). All rights reserved.

Perfect balance in total knee arthroplasty: The elusive compromise

A Tensor/Balancer device (Stryker Howmedica Osteonics, Allendale, NJ) was used to restore optimal stability and alignment during 83 consecutive total knee arthroplasties with a minimum of 6-week clinical and radiographic follow-up. The surgical technique is described. Mean flexion-extension symmetry was restored to within 1[deg ]. Mean femoral rotation required to achieve symmetry in flexion differed between varus (4.38[deg ]) and valgus (6.0[deg ]) knees. Of 83 knees, 7 had [gt ]3 mm of subjective laxity during component trialing and were associated with a preoperative deformity of [gt ]15[deg ]; 19 knees required femoral rotation of [gt ]6[deg ] and were associated with greater preoperative malalignment. Postoperative knee alignment, range of motion, Knee Society score, and lateral release rate were similar between the 2 groups. The use of a Tensor/Balancer device in total knee arthroplasty can achieve outcomes comparable to existing techniques with potential for improved technical accuracy.

Model-based Roentgen stereophotogrammetry of orthopaedic implants

Attaching tantalum markers to prostheses for Roentgen stereophotogrammetry (RSA) may be difficult and is sometimes even impossible. In this study, a model-based RSA method that avoids the attachment of markers to prostheses is presented and validated. This model-based RSA method uses a triangulated surface model of the implant. A projected contour of this model is calculated and this calculated model contour is matched onto the detected contour of the actual implant in the RSA radiograph. The difference between the two contours is minimized by variation of the position and orientation of the model. When a minimal difference between the contours is found, an optimal position and orientation of the model has been obtained. The method was validated by means of a phantom experiment. Three prosthesis components were used in this experiment: the femoral and tibial component of an Interax total knee prosthesis (Stryker Howmedica Osteonics Corp., Rutherfort, USA) and the femoral component of a Profix total knee prosthesis (Smith & Nephew, Memphis, USA). For the prosthesis components used in this study, the accuracy of the model-based method is lower than the accuracy of traditional RSA. For the Interax femoral and tibial components, significant dimensional tolerances were found that were probably caused by the casting process and manual polishing of the components surfaces. The largest standard deviation for any translation was 0.19 mm and for any rotation it was 0.52°. For the Profix femoral component that had no large dimensional tolerances, the largest standard deviation for any translation was 0.22 mm and for any rotation it was 0.22°. From this study we may conclude that the accuracy of the current model-based RSA method is sensitive to dimensional tolerances of the implant. Research is now being conducted to make model-based RSA less sensitive to dimensional tolerances and thereby improving its accuracy.