We appreciate Dr. Warner’s response to our publication(1) and acknowledge his experience and expertise in this field. We assure the readership that our initial reactions to the observations we published were similar. In fact, a delay in recognition of the condition and potential etiology occurred for this very reason. Based on early reports of chondrolysis after shoulder arthroscopy, we had already explained to one of the patients that her condition has been seen and reported by others, but was of unknown etiology and apparently not able to be helped by further surgery. The only reason she and we decided to proceed with a diagnostic arthroscopy is that neither she nor we were content to assume the cause could not be figured out.

A saying that we have heard attributed to the late Dr. Paul Brand is, “When the observations don’t fit the theory, question the theory”. Once we saw the pristine cartilage sharply and unequivocally demarcated from the area of completely destroyed cartilage, and the suture anchors poking out of the holes in the glenoid (where they were scraping the humeral head), we realized that the damage had to have resulted from mechanical abrasion of the humeral head. On the same day, just before we re- arthroscoped that first patient, we had performed the index surgery on patient #2. His father, who is an orthopedic surgeon, trained with us. I told him of my startling observation and suggested we watch his son’s shoulder carefully and get a CT scan, if in doubt, at an early stage. Eight weeks post-operatively he developed progressive shoulder pain with motion and his CT scan suggested a small lesion around 2 anchors. Three months post-op the lesions had enlarged and we scoped him, confirming anchor pull-out and erosion against the humeral head with exactly the same demarcation between pristine and destroyed cartilage.

As stated and schematically illustrated in Figure 5 of our publication(1), we believe that several factors (including multiple anchors) interact to cause the problem seen in the patients we reported. However, it would be impossible to explain the observations based on theories relating to infection or the adverse effects of the use of radiofrequency. We only used radiofrequency in 3 patients. It was used for no more than 2 to 3 seconds, and only to congeal the shaved surface of an undersurface rotator cuff tear. Furthermore, it was used on the lowest setting each time and with high volume irrigation to prevent overheating of fluid.

As a recognized authority in the cartilage field, with a formal Ph.D, as well as two and half decades of experience, the senior author feels confident in recognizing patterns of cartilage damage due to chemical or cytokine mediation versus mechanical factors. While surgical technique may have been a factor, the senior author is experienced in shoulder arthroscopy and has never had this problem with other anchor designs before or since using the Mitek Bioknotless anchor. We recognize the implications of our findings, and so did the reviewers and editors of the Journal who were thorough in cross-examining the evidence before accepting it.

Reference:

1. Athway GS, Shridharani SM, O'Driscoll SW. Osteolysis and arthropathy of the shoulder after use of bioabsorbable knotless suture anchors. A report of four cases. J Bone Joint Surg. Am. 2006;88:1840-1845.

To The Editor:

The authors of the article, "Osteolysis and arthropathy of the shoulder after use of bioabsorbable knotless suture anchors. A report of four cases"(1) present four cases in which the use of Bioabsorbable Knotless Suture anchors are implicated as the etiology of postoperative arthrosis. I have used this particular anchor over the past five years and have not observed any such cases. I am particularly concerned with their observations. I am troubled by their conclusions and the reasons for this are as follows. In Cases 1, 2, and 4, the authors acknowledge using Thermal Ablation “sparingly” in addition to placement of the five suture anchors. Certainly, use of thermal energy presents a confounding variable which has been associated with chondral injury in prior literature. In case 3, Proprionibacterium acnes was cultured, but the authors dismissed this as a possible cause of arthrosis and implicated use of the anchors instead.

The authors go on in their discussion section to conclude that the anchor has a propensity for loosening and that other factors such as cellular reaction to the poly (L-lactide) are a possible factor. In addition, they indicate that the five drill holes they created to place the anchors may have resulted in an environment which promoted loosening of the anchors. I agree that all these factors may have played a role in implant failure.

In the same issue of JBJS, Boileau and co-workers (2) make the point that use of more than three anchors is associated with successful surgery. All the anchors they used were also poly (L-lactide) and they experienced no adverse events. My personal experience has been the use of these anchors for over 200 arthroscopic Bankart or Superior Labrum repairs with no adverse events. Mitek has sold 186,195 Bioknotless anchors worldwide since its launch. They have received a total of 123 complaints (0.066%). There are only six reported complaints regarding synovitis, osteolysis, or articular cartilage damage (0.003%), including the four from Dr. O'Driscoll(1).

In conclusion, the confounding variables which make it difficult to agree with the authors' conclusions are use of thermal ablation, culture of Proprionobacterium acnes from one wound, surgical technique, and the possibility for mechanical failure due to multiple drill holes.

The author(s) of this letter to the editor did not receive payment or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author(s) are affiliated or associated.

References:

1. Athwal GS, Shridharani SM, O'Driscoll, SW. Osteolysis and arthropathy of the shulder after use of bioabsorbable knotless suture anchors. A report of four cases. J Bone Joint Surg Am. 2006;88:1840-1845.

2. Boileau P, Villalba M, Hery JY, Balg F, Ahrens P, Neyton L. Risk Factors for Recurrence of shoulder instability after arthroscopic bankart repair. J Bone Joint Surg Am. 2006;88:1755-1763.