Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 25, Issue 6 , Page 701, June 2009

An Intrinsic Flaw With Current Bioabsorbable Polymer Devices?

Biocomposites Ltd., Keele, Staffordshire, England

Article Outline

 

To the Editor:

I have read with interest the recent article by Andrew Wallace and colleagues1 entitled “Glenoid Rim Fracture in Contact Athletes With Absorbable Suture Anchor Reconstruction.” The article details 3 sentinel cases of what could be, potentially, an intrinsic flaw with current bioabsorbable polymer devices.

A number of recent long-term clinical studies have shown that polymer devices used in anterior cruciate ligament (ACL) surgery have not, as originally anticipated, been replaced by bone upon biodegradation of the implant.2 Fibrous encapsulation of polymer implants is a routinely observed phenomenon in animal implantation studies, preventing bony infiltration of the site and subsequent ossification.3 Although, in ACL surgery, replacement by bone is desirable to facilitate potential revision surgery, in a smaller bone with the potential for repeat trauma, an implant that does not detrimentally affect the intrinsic strength and stability of the bone could be considered essential. A return to metal devices remains undesirable because of the problems associated with imaging artifacts, stress shielding, and migration. Furthermore, in instances of potential repeat trauma, as with impact athletes, an implant with a much higher modulus than the surrounding bone could provide a significant stress riser, potentially contributing to a fracture.

Recently, a number of calcium-polymer composite suture anchor devices have been introduced for glenoid instability and rotator cuff repair indications. The introduction of calcium particles within polymer both improves local bone apposition and subsequent infiltration as absorption takes place and provides greater modulus matching to the surrounding bone. Furthermore, the alkaline nature of the calcium salts may provide pH buffering against the acidic degradation byproducts of the polymer. Recent articles from both animal studies4 and long-term clinical results in ACL surgery5 have shown the potential of such composite materials compared with polymer alone when used in ACL repair devices. These results pave the way for cautious optimism, although history has shown, of course, that an excellent result with a specific material in an animal study or for another seemingly relevant clinical indication does not necessarily translate accordingly in practice.

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References 

  1. Banerjee S, Weiser L, Connell D, Wallace AL. Glenoid rim fracture in contact athletes with absorbable suture anchor reconstruction. Arthroscopy. 2009;25:560–562
  2. Barber FA, Dockery WD. Long-term absorption of poly-L-lactic acid interference screws. Arthroscopy. 2006;22:820–826
  3. Williams DF. Biocompatibility principles. In: The encyclopedia of materials: Science and technology. Amsterdam: Elsevier; 2004;p. 542–548
  4. Hunt JA, Callaghan JT. Polymer-hydroxyapatite composite versus polymer interference screws in anterior cruciate ligament reconstruction in a large animal model. Knee Surg Sports Traumatol Arthrosc. 2008;16:655–660
  5. Barber FA, Dockery WD. Long-term absorption of β-tricalcium phosphate poly-L-lactic acid interference screws. Arthroscopy. 2008;24:441–447

PII: S0749-8063(09)00202-3

doi:10.1016/j.arthro.2009.03.006

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  • Author's Reply

    Andrew L. Wallace, Lori Weiser, Sughran Banerjee
    Arthroscopy: The Journal of Arthroscopic and Related Surgery June 2009 (Vol. 25, Issue 6, Pages 701-702)

Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 25, Issue 6 , Page 701, June 2009

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