Overall outcomes the same; functional scores better at 6 weeks
Patients managed with early weight bearing (EWB) following arthroscopic microfracture for osteochondral lesions of the talus exhibited significant improvement in early postoperative functional scores compared to those managed with delayed weight bearing (DWB), according to research presented by CPT J. Banks Deal Jr, MD, of Tripler Army Medical Center, Honolulu, Hawaii at the 2016 annual meeting of the Society of Military Orthopaedic Surgeons (SOMOS). This finding was not associated with any significant differences in functional scores or pain at any other time points.

Dr. Deal and his fellow investigators conducted the study to determine "what clinical consequence, if any, would occur if early weight bearing was allowed after microfracture for an osteochondral lesion of the talus."

They hypothesized there would be no difference in subjective patient outcome scores between EWB and DWB after microfracture for an osteochondral lesion of the talus. This was based in part on their experience with some patients who admitted to noncompliance with non–weight–bearing (NWB) directives (traditionally 6 to 8 weeks), yet had acceptable clinical outcomes. Also, Dr. Deal said, some recent research had indicated that EWB might not have detrimental effects.

Conducting the study
Thirty-seven patients took part in the prospective, randomized trial. Enrolled subjects had unilateral, primary, unifocal osteochondral lesions treated with arthroscopic microfracture.

"Of note, we excluded patients with multiple lesions, lesions larger than 1.5 square centimeters, and ipsilateral ankle fractures," Dr. Deal said.

The patients were randomized into EWB (17 patients) and DWB (20 patients) cohorts at their 2-week visit after surgery. Both cohorts were managed with rigid immobilization and non–weight-bearing status after surgery. Subjects in the EWB group began weight bearing as tolerated at 2 weeks, whereas those in the DWB group were instructed to remain strictly NWB on crutches for an additional 4 weeks. Both groups were placed into removable fracture boots so that the physical therapists could work on ankle range of motion. Primary outcome measures included Foot and Ankle Outcomes Questionnaire scores (AAOS scores)—derived from the questionnaire developed by the AAOS and various orthopaedic specialty societies—and the Numeric Rating System (NRS) pain score. Both scores were collected preoperatively as well as at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperatively.

There were no differences between the two cohorts in terms of patient age, mechanism of injury, lesion size, lesion stage, or baseline NRS or AAOS scores. The mean age at surgery was 34.1 years (range, 21–50 years). Seventy percent of the lesions were lateral, 22 percent were medial, and the remainder were central. The EWB group demonstrated statistically significant improvement in AAOS scores at 6-week follow-up, compared to the DWB group (mean 83.1 versus 68.7, P = 0.017). There were no significant differences in AAOS score between the EWB and DWB groups at the other time points (Fig. 1). NRS pain scores were not significantly different between the EWB and DWB groups at any time point (Fig. 2). At 1-year follow-up, the EWB group's AAOS scores were not significantly different from that scale's uninjured, normative population; however, at all other time points these patients had significantly lower scores than their uninjured counterparts.

Dr. Deal noted that osteochondral lesions of the talus are "common injuries," occurring in up to 50 percent of ankle sprains and 66 percent of ankle fractures.

"When nonsurgical management fails to relieve patients' symptoms, arthroscopic microfracture has been shown to yield good to excellent results in many patients, though outcomes may deteriorate over time," he said.

Postoperative protocols reported in the literature typically involve 6 to 8 weeks of NWB status.

"This delayed weight-bearing period is intended to protect the microfracture site as a callous forms and remodels into fibrocartilage, but it can be onerous to patients," Dr. Deal said.

The question of weight bearing
Delayed weight-bearing protocols after microfracture were first challenged in the knee literature, noted Dr. Deal. A 2005 study by Marder et al showed equivalent outcomes between early and delayed weight bearing at 2-years follow-up after microfracture of the femoral condyles.

Prior to this study, noted Dr. Deal, there had been one prospective study comparing early and delayed weight-bearing protocols after microfracture for osteochondral lesions of the talus. Lee et al of South Korea published a prospective randomized trial of 81 patients who underwent arthroscopic microfracture for osteochondral lesions of the talus and were managed with early or delayed weight-bearing protocols.

"They showed noninferiority from 3-month to 2-year follow-up, but they did not capture the 6-week time point," Dr. Deal said.

"We found that functional outcomes at the 6-week visit were improved with early weight bearing," he said. "This was associated with no significant differences in pain or function at other time points. Our results are consistent with the prior study by Lee et al, with the exception that their study did not capture this improvement at the 6-week time point."

Outcomes in both function and pain scores deteriorated at the 2-year point, noted Dr. Deal, who also explained that this finding matches that of a study by Ferkel et al in which 35 percent of patients experienced a decrease in outcome scores over time.

"In our study, both groups followed this pattern, but were not significantly different from each other," Dr. Deal said. He and his fellow authors wrote, "At final follow-up, all patients showed outcomes that were inferior to the baseline, uninjured population. This long-term trend suggests that the fibrocartilage formation induced by microfracture may not affect a durable repair for all patients. We know that fibrocartilage degradation is shown at 1-year follow-up and outcomes tend to decrease over time. This may be especially true in active military populations."

They also noted that "the effect of prolonged non–weight bearing after surgery for lower extremity injuries has been found to decrease patient-reported RAND-36 scores, which assess physical function, vitality, social function, and role-emotional status. Prior studies addressing Achilles tendon ruptures and osteochondral lesions of the knee treated with microfracture have shown no increase in complications, and improvement in RAND-36 scores after EWB."

Limitations of this study, Dr. Deal said, include multiple operating surgeons, with possible variability of technique.

"Arthroscopic microfracture of osteochondral lesions of the talus is a relatively straightforward procedure, and all surgeons were fellowship trained, so we consider this to be a small limitation," he noted. "Secondly, our population was predominantly, young, male, and athletic, which must be taken into account when applying the results of this study to other groups. Additionally, we only report 2-year follow up, and attrition at final follow-up meant that we could show no significant difference but not noninferiority as was demonstrated by Lee et al. The primary contribution of this study to our current body of knowledge is the demonstration of early postoperative period functional gains with early weight bearing."

Because function seems to degrade over the longer term, further study should investigate optimal rehabilitation protocols after surgery for these injuries, Dr. Deal said.

Dr. Deal's coauthors are Adam T. Groth, MD; Paul M. Ryan, MD; Thomas C. Dowd, MD; Kevin L. Kirk, DO; Jeanne C. Patzkowski, MD; Patrick M. Osborn, MD; Claude D. Anderson, MD; and James R. Ficke, MD.

The authors' disclosure information can be accessed at www.aaos.org/disclosure

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

• A single prior study and anecdotal evidence suggested that early (2-week) weight bearing after microfracture surgery for the talus would not yield poorer outcomes than delayed (6-week) weight bearing, which can be onerous for patients.
• In this randomized study of 37 patients, the early and delayed weight-bearing patients had similar results at all time periods, except at 6 weeks, at which time the early group demonstrated improved functional outcome scores.
• Fibrocartilage formation induced by microfracture may not affect a durable repair for all patients, and outcomes may worsen over time. Patients had worse function at 2 years compared to their uninjured counterparts.
• Study limitations included the fact that most of the patients in this study were young, male, and athletic.

References:

1. Marder, RA, Hopkins G Jr, Timmerman, LA: Arthroscopic microfracture of chondral defects of the knee: A comparison of two postoperative treatments. Arthroscopy 2005;21(2):152–158.
2. Lee KB, et al: Second-look arthroscopic findings and clinical outcomes after microfracture for osteochondral lesions of the talus. Am J Sports Med 2009;37 Suppl 1:63S–70S.
3. Ferkel RD, et al: Arthroscopic treatment of chronic ostechondral lesions of the alus: Long-term results. Am J Sports Med 2008;36:1750–1763.