SLR - October 2016 - Rachel Hutchins

The Importance of Sufficient Graft Material in Achieving Foot or Ankle Fusion

Reference: DiGiovanni CW, Lin SS, Daniels TR, Glazebrook M, Evangelista P, Donahue R, Beasley W, Baumhauer JF. The Importance of Sufficient Graft Material in Achieving Foot or Ankle Fusion. J Bone Joint Surg Am. 2016 Aug 3;98(15):1260–7.
 
Scientific Literature Review
 
Reviewed By: Rachel Hutchins, DPM
Residency Program: St. Vincent Hospital and Worcester Medical Center, Worcester, MA
 
Podiatric Relevance: This article addresses the concern of fusion rates for foot and ankle arthrodesis surgeries with bone grafting (autograft and allograft). This is of great importance to the podiatric surgeon in order to reduce unsatisfactory outcomes in fusions. Whatever can be done to increase fusion rates must be done and in order to know these methods, literature like this must be taken into consideration. What is also interesting is that the authors increased the qualification for fusion by using the parameter of >50 percent of the joint having bony trabeculation versus previous parameters of 25 to 49 percent, which had been previously correlated with clinically successful fusions. The authors’ main hypothesis was that having the adequate amount of graft material, which was defined as >50 percent of the cross-sectional area of the arthrodesis site, would increase fusion in ankle and hindfoot arthrodeses.  

Methods: The study encompassed 379 patients with a total of 573 joints. This was a retrospective analysis of a prospective trial. The timeframe was April 2007 to January 2010. Nonunion risk factors, such as diabetes, BMI>30, smoking and revisional surgery, were taken into account. Surgical site (ankle or hindfoot) was also noted. The patients who had undergone grafting were recorded as having either augment bone graft or autograft harvested from various areas of the patients’ bodies. The amount of graft material used was measured and recorded. The outcome was initially determined by CT evaluation at nine and 24 weeks. At nine weeks, the amount of graft fill was determined to be “adequate” meaning graft material occupied 50 to 100 percent of the joint space or “inadequate” with graft material occupying <50 percent. At 24 weeks, another CT was acquired to assess the amount of bony bridging. This was calculated in the same manner as the nine-week CT scan that evaluated the amount of graft fill. Fusion was declared if >50 percent of the joint articulation was bridged by osseous trabeculation. The CT scans were interpreted by the same radiologists who had originally assessed the nine-week CT scans. At 52 weeks, the arthrodesis was determined to be clinically successful, including clinical examination, radiographic evaluation, functional outcome scores and no need for revisional surgery. This was determined by the original surgeons.

Results: At nine weeks, the CT scans of the 573 joints was obtained with 472 (82 percent) having >50 percent of the joint space filled with graft material. One hundred and one joints (18 percent) had less than adequate results with <50 percent of joint space being filled with graft material. At 24 weeks when the CT scan was repeated, 383 (81 percent) of the 472 with adequate filling of graft material demonstrated >50 percent of joint surface being bridged with bony trabeculation resulting in successful fusion. Of the 101 joints that had inadequate filling of graft material, 21 (21 percent) demonstrated >50 percent of the joint surface being bridged with bony trabeculation resulting in successful fusion. Overall, of the 404 joints that were successfully fused, 383 (93 percent) had adequate graft fill and 21 (5 percent) did not. The clinical evaluation at 52 weeks determined 497 (87 percent) of the 573 joints were clinically fused. Of these 497, 424 were from the adequately filled graft group with 73 being from the inadequately filled graft group.

Conclusions: The authors concluded that there was no significant difference in fusion rates between the various arthrodeses being performed whether on ankle, subtalar, calcaneocuboid or talonavicular joints. There was no significant difference between graft material that was used, graft harvest site, number of joints fused, sex, age, BMI, history of diabetes or smoking status. The main significant difference in fusion rates was found to be whether or not the amount of graft material placed was adequate or not based on the parameters previously stated. Eighty percent of joints with adequate graft fill achieved successful fusion. Twenty percent of joints with inadequate graft fill achieved successful fusion. There was a significantly lower fusion rate in those patients who had previous bony surgery on the joints fused. There was also a significant difference in fusion rates between patients with osteoarthritis vs. those with rheumatoid arthritis with those patients having rheumatoid arthritis having a much greater successful fusion rate. The authors supported their hypothesis that fusion would occur at a more successful rate with a greater contact area of grafting material within an arthrodesis site. It is not so much the fact that there was increased fusion with more graft material that was interesting but the fact that the patients’ comorbidities did not affect the results in a significant manner. Having the breakdown of fusion rates between the various arthrodesis sites, even though they reported it as being insignificant, would be valuable. They also did not mention how they came to measure the greater than or less than 50 percent cross-sectional area they were using as their parameter for adequate vs. inadequate graft filling as well as fusion. Nor if they primarily used one specific view of the CT or multiple views and if taking the average of those to calculate the cross-sectional area would add value to the calculation of the 50 percent area. Moreover, it is very difficult to visualize a joint space to the point where, in the operating room, the surgeon can determine whether or not a premeasured amount of grafting material is taking up more than 50 percent of that space. The main aspect of this study that is important to incorporate into patient care is to not automatically be dissuaded by those patients who have multiple comorbidities as they are just as likely to have a successful outcome as those patients who have none. It is necessary to take care when placing grafting material and not put so much weight as to the type of grafting material used. Considering the complications that can arise with autologous bone grafting, it would be better to use allograft material based on the results of this study.  

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