Assessment of the equivalence of a generic to a branded femoral stem

Outcomes and Cost Comparison Between Generic and Conventional Cephalomedullary Nails in the Treatment of Peritrochanteric Femur Fractures

INTRODUCTION

Although generic orthopaedic implants have been available for several years, there has been slow adoption of this cost-saving option. We hypothesize equivalent outcomes between generic and conventional cephalomedullary nails (CMN) in the treatment of peritrochanteric femur fractures.

METHODS

We evaluated 419 patients undergoing CMN for peritrochanteric femur fracture with a minimum 6-month follow-up. Demographic data, radiographic assessment, and clinical outcomes were compared.

RESULTS

Ninety patients were treated with generic implants and 329 patients with conventional implants. The overall complication rate was 7.0%, with a revision surgery rate of 5.4%. No significant differences were seen in demographic variables or surgical factors. Although there was an increased incidence of postoperative infections with conventional nails (P = 0.045), no significant differences were seen in other complications.

CONCLUSION

At our institution, generic nails cost approximately 38% less than their conventional counterparts. There seems to be no increased rate of implant-associated complications with the use of generic CMNs, although allowing for notable cost savings.

High rates of implant fracture of a generic polished tapered femoral stem

OBJECTIVES

Cemented polished tapered stems have demonstrated excellent long-term outcomes. Based on this concept, many generic tapered stems have been released into the market. The aim of this study was to evaluate implant-related complications of 1 specific stem design.

METHODS

Between 2010 and 2017, 315 total hip replacements were performed using a Fortress stem (Biotechni, La Ciotat, France). Patient records and radiology were retrospectively reviewed for implant-related complications. A failure analysis was performed on the failed Fortress stems in order to determine the cause of premature failure.

RESULTS

7 (2.2%) patients sustained a fracture of the neck of the implant after a mean of 5 years (range 50-81 months). All fractures were atraumatic, originating at the introducer inlet of the stem. All fractured occurred in obese patients (BMI >33 kg/m²) with a small sized prosthesis. Of these, there were 5 135° and 2 125° stems. Fracture risk was 23% (7/30) for patients with a small sized stem and a BMI >30 kg/m². All cases were revised using a cement-in-cement technique or a cementless modular revision stem. Failure analysis on the retrieved stems revealed a stress riser at the bottom of the introducer inlet.

CONCLUSIONS

An alarmingly high rate of early implant fractures was seen using this specific type of cemented stem, particularly when using smaller implant sizes in obese patients. Although based on a proven design, a specific modification led to a stress riser in the neck area, which resulted in a high incidence of implant failure. This series underlines the importance of a stepwise introduction into the market of new orthopaedic devices even when based on established concepts. Generic stems may not behave as the original stem upon which it was designed.

A retrieval analysis of the Precice intramedullary limb lengthening system

OBJECTIVES

The Precice nail is the latest intramedullary lengthening nail with excellent early outcomes. Implant complications have led to modification of the nail design. The aim of this study was to perform a retrieval study of Precice nails following lower-limb lengthening and to assess macroscopical and microscopical changes to the implants and evaluate differences following design modification, with the aim of identifying potential surgical, implant, and patient risk factors.

METHODS

A total of 15 nails were retrieved from 13 patients following lower-limb lengthening. Macroscopical and microscopical surface damage to the nails were identified. Further analysis included radiology and micro-CT prior to sectioning. The internal mechanism was then analyzed with scanning electron microscopy and energy dispersive x-ray spectroscopy to identify corrosion.

RESULTS

Seven male and three female patients underwent 12 femoral lengthenings. Three female patients underwent tibial lengthening. All patients obtained the desired length with no implant failure. Surface degradation was noted on the telescopic part of every nail design, less on the latest implants. Microscopical analysis confirmed fretting and pitting corrosion. Following sectioning, black debris was noted in all implants. The early designs were found to have fractured actuator pins and the pin and bearings showed evidence of corrosive debris. The latest designs showed evidence of biological deposits suggestive of fluid ingress within the nail but no corrosion.

CONCLUSION

This study confirms less internal corrosion following modification, but evidence of titanium debris remains. We recommend no change to current clinical practice. However, potential reuse of the Precice nail, for secondary limb lengthening in the same patient, should be undertaken with caution.Cite this article: V. C. Panagiotopoulou, K. Davda, H. S. Hothi, J. Henckel, A. Cerquiglini, W. D. Goodier, J. Skinner, A. Hart, P. R. Calder. A retrieval analysis of the Precice intramedullary limb lengthening system. Bone Joint Res 2018;7:476-484. DOI: 10.1302/2046-3758.77.BJR-2017-0359.R1.