From Bench to Bedside: Synthesizing Better Replacements and Reconstructions

Total joint replacement surgery represents a resounding success and one of the major medical breakthroughs of the last century. While we continue to grapple with relatively uncommon but severe complications such as infection and instability, total joint replacement is our mainstay that helps restore function and quality of life for hundreds of thousands of patients each year in the United States alone. It also represents virtually the only true success of its kind. Collectively, our track record for the artificial or synthetic replacement of almost any other musculoskeletal structure has been disappointing, at best. We fail—a lot.

Let’s start with artificial ACL replacement. Nearly 34% of Dacron (Deknatel, Fall River, MA, USA) ACL reconstructions developed recurrent instability, while 28% of patients receiving the Gore-Tex (W. L. Gore & Associates, Newark, DE, USA) version developed synovitis and arthrosis [1]. Other synthetic graft types did little better, with frequent rupture, recurrent laxity, synovitis, and arthritis [1, 3, 5, 10]. Synthetic total meniscal replacements and spacers? Ditto [4]. I could go on. And while not, perhaps, an “epic fail” like synthetic ligaments, lumbar disk replacement, at first hailed as the motion-preserving solution to axial back pain and fusion complications, has hardly taken over the world [7].

We shouldn’t necessarily be surprised by these results, as these attempts fly directly in the face of the plastic surgery dictum of “replacing like with like.” But we shouldn’t be unduly discouraged, either. Sir John Charnley started out with an astronomical 8.9% of total hip replacement infections, but he was able to persevere and reduce this to remarkably close to our current levels (1.3%) in just a few short years; for his success in this regard, he was knighted [2]. But we do need to get smarter about our approach to these problems.

A few more-recent attempts make better sense. In general, these devices and techniques seek to augment repairs of biologic tissue or scaffold-based reconstructions rather than permanently, artificially replace what is damaged or missing. For example, Ligament Advanced Reinforcement System (LARS; Surgical Implants and Devices, Arc-sur-Tille, France)-augmented knee ligament reconstructions cause synovitis in a dramatically lower percentage of patients (1% - 2.6%) than other synthetic ligaments [1] and, in some series, have equivalent or better functional and stability outcomes than quadrupled hamstring grafts [6]. Critically, the LARS system is seeking to confer early stability, early return to sport, and protect the biologic reconstruction or repair until adequate healing has occurred; it is not a fake ligament that is supposed to last forever. Afterall, intramedullary nails aren’t replacing the fractured bone, they are attempting to stabilize the fracture and share load until healing occurs; if healing never happens, the nails eventually and predictably break.

We have seen other examples of this. Synthetic meniscal replacement did not work well, but porous meniscal scaffolds show promising results with only 6.1% of more than 600 patients requiring revision [4] and evidence of biologic, fibrous replacement on magnetic resonance imaging and second-look arthroscopy. Modified Broström procedures augmented with an internal brace have demonstrated equivalent clinical outcomes and earlier return to sport than un-augmented procedures [11]. High-grade acromioclavicular joint separations and distal clavicle fractures are increasingly undergoing stabilization with ultra-high strength suture or tape and likewise reflect good clinical results [8]. In each of these cases, we would expect mechanically stable and durable reconstructions because in each instance there is a repaired ligament, a reconstructed ligament, or a broken bone which can heal and then last.

Each of these advances is at least modestly noteworthy in its own right and, in general, represents good news for our technical toolboxes and our patients. But what is really going on (I hope) is that we are finally getting smarter about how we approach these problems. Not every new idea, technique, or device is going to work and hold up to scientific scrutiny or, that ever-lurking destroyer of dreams of grandeur, clinical follow-up. However, we need to continue this trend and be mindful of past fiascos, flops, and disappointments, lest we come to embody Einstein’s definition of insanity. Of course, that didn’t work … again.