Donor-site morbidity from harvesting autologous bone graft has driven the decades-long search for a substitute that performs at least as well as a patient’s own bone. Much of the clinical research on donor-site morbidity is flawed by detection bias, but other factors such as operating-room time and expense are still driving the search for the ideal substitute for autologous bone. Still, the discovery of an ideal bone-graft substitute continues to be elusive.
In The November 6, 2019 issue of The Journal, Myerson et al. report findings from a Level-I trial that investigated the use of adipose-derived cellular bone matrix (ACBM) as a graft substitute in patients undergoing subtalar arthrodesis. Among 57 patients who received autograft and 52 who received ACBM, the substitute delivered lower fusion rates as determined by both CT and plain radiographic/clinical evaluations at 6 months. In addition, patients treated with autologous bone graft had lower rates of serious adverse events.
I commend the authors and funders (AlloSource) of this well-designed clinical trial for reporting these negative results, because it is often just as important to know what doesn’t work as what does. (This manuscript was submitted even after AlloSource decided to halt further production of its ACBM product in 2017.) Such transparent reporting saves other investigators and graft substitute-focused companies from going down similar avenues of investigation. Perhaps even more importantly, publishing negative results such as this might save patients from undergoing procedures with similar formulations that would probably have minimal chance of helping and could do harm.
By contributing to the scientific “process of elimination,” this study brings us one step closer to the identification of a worthy substitute for autologous bone graft.
Marc Swiontkowski, MD
Health-related quality of life (HRQOL) in adulthood is an important outcome measure for patients diagnosed with juvenile or adolescent idiopathic scoliosis. In the May 16, 2018 issue of The Journal of Bone & Joint Surgery, a cross-sectional study of 1,187 Swedish patients with scoliosis by Diarbakerli et al. reveals patient-reported HRQOL outcomes at an average follow-up of approximately 18 years. Using the Scoliosis Research Society-22r (SRS-22r) and the EuroQol 5-Dimensions (EQ-5D) instruments, the authors analyzed outcomes among those who had been untreated (n = 347), brace-treated (n = 459), or surgically treated (n = 381) in accordance with standards at the time of diagnosis.
The surgically treated group had significantly lower scores in the SRS-22r domains of function and self-image, compared with the scores in those domains among the other two groups. According to Daniel J. Sucato, MD, who commented on the study, those findings “most likely reflect the various effects of the surgical procedure, including the stiffness imparted by the arthrodesis of the spine,… stiffness of the soft tissues, and the presence and awareness of implants and a surgical incision.” Diarbakerli et al. also found that untreated patients did not report a decrease in HRQOL with age.
Interestingly, patients treated surgically had higher SRS-22r satisfaction-domain scores than brace-treated patients, even though overall SRS-22r and EQ-5D scores were lower among surgically treated patients than brace-treated patients. For spine surgeons, one key finding was that “a more caudal extent of fusion may be one of the most important characteristics that negatively affects quality of life” in patients undergoing scoliosis surgery.
With its large number of patients and long-term, patient-focused outcomes, this study generally corroborates findings from previous, smaller studies. But, as Dr. Sucato points out in his commentary, “the brace and surgical groups had treatments that were current at the time but not relevant today, especially as they involved the use of first-generation techniques and instrumentation.”
In the December 7, 2016 issue of JBJS, Krause et al. analyze data from a 2013 industry-sponsored RCT to investigate correlations between nonunions of hindfoot/ankle fusions indicated by early postoperative computed tomography (CT) and subsequent functional outcomes. Whether nonunion was assessed by independent readings of those CT scans at 24 weeks or by surgeon composite assessments at 52 weeks, patients with failed healing had lower AOFAS, SF-12, and Foot Function Index scores than those who showed osseous union.
This study suggests that a CT should be obtained from patients who are at least 6 months out from a surgical fusion and are not progressing in terms of activity-related pain and function. Depending on the specific CT findings, a repeat attempt at bone grafting, with the possible addition of bone-graft substitute and/or possible modification of internal fixation, may be warranted to forestall later clinical problems.
Krause et al. imply that trusting plain radiographs that show no indication of fusion failure is not acceptable when patient pain and function do not improve in a timely fashion. Conversely, they conclude that their findings do not support “the concept of an asymptomatic nonunion (i.e., imaging indicating nonunion but the patient doing well),” because nonunions identified early by CT eventually resulted in worse clinical outcomes. The authors also noted that obesity, smoking, and not working increased the risk of nonunion, corroborating findings from earlier studies.
While advanced imaging such as CT is not necessary in foot/ankle fusion patients who are improving in terms of function, pain, and swelling , this study stresses the importance of achieving union following these fusion procedures.
Marc Swiontkowski, MD
A therapeutic Level II study by DiGiovanni et al. in the August 3, 2016 edition of The Journal of Bone & Joint Surgery examined the relationship between successful foot/ankle fusions and the amount of graft material used. The authors found that among 573 procedures in which graft material (either autograft or AUGMENT bone graft) occupied ≥50% of the cross-sectional fusion space at nine weeks, 81% were successfully fused at 24 weeks. However, among 101 procedures with <50% of the graft space filled, only 21% were successfully fused at 24 weeks.
The authors determined both graft-fill percentages at nine weeks and fusion success at 24 weeks using CT scans. The percentage of graft fill was estimated by mental summation of graft fill present in each individual CT slice of the joint, and joint fusion was determined by measuring the percentage of osseous bridging in the same semiquantitative manner.
The significant fusion rate differences between joints with and without ≥50% graft fill were consistent regardless of whether autograft or allograft was used and regardless of which joint was fused. The authors conclude that these findings “demonstrated that when a surgeon can eliminate bone-to-bone gaps in any joint intended for fusion,…such a joint has a significantly better chance of ultimately achieving fusion,” although they caution against “overpacking a joint with excessive graft material.” DiGiovanni et al. cite the need for further research “to determine the ideal amount of graft material required for a clinically relevant and impactful effect on fusion” and to help develop “graft materials that are easier to introduce and can be more precisely inserted into the intended fusion space.”
In the December 16, 2015 edition of The Journal, Pellegrini et al. present the results from a cohort of 23 patients who had initially undergone ankle arthrodesis and then, due to decreasing function and increasing mid- and hindfoot pain, sought relief via conversion to an ankle arthroplasty. The good news is that this conversion provided meaningful clinical improvement in pain and function, with 87% survival of the implants over the mean 33-month follow-up.
One technical detail the authors recommend is prophylactic fixation of the malleoli as a concomitant procedure, noting that local osteopenia related to arthrodesis make malleoli prone to fracture during insertion of the tibial component. It is difficult to determine if these conversions were necessitated by poor surgical technique during the original arthrodesis, but I suspect in some cases they were. Also, considering the arthritic changes to the mid- and hindfoot joints related to arthrodesis, it is easy to understand that patients would benefit from the takedown of the fusion and return of some ankle motion to diminish the stress on those joints.
Reflecting on the findings from this clinical cohort series has prompted me to change my surgical technique for ankle arthrodesis. Formerly I hemi-sected the lateral malleolus and fixed it to the talus and distal tibia. Now I preserve the distal fibula, ensure removal of all cartilage in the medial and lateral gutters, add bone graft, and provide fixation with cancellous lag screws. This change in technique facilitates takedown of the fusion and conversion to ankle arthroplasty if necessary in the future. In my opinion, the clarion call now for ankle arthrodesis must be “save the fibula!”
Marc Swiontkowski, MD