Displaced intra-articular calcaneal fractures: variables predicting late subtalar fusion.

OBJECTIVE: The goal of the current study was to analyze the prospective clinical outcome of patients who failed closed or open treatment of a displaced intra-articular calcaneal fracture. This cohort of patients required a secondary subtalar fusion by distraction bone-block arthrodesis.

DESIGN: Review of prospective, randomized trial database.

SETTING: Four level I trauma centers.

PATIENTS: Between April 1, 1991 and December 31, 1997, 424 patients with 471 displaced intra-articular calcaneal fractures were involved in a large, multicenter, randomized trial. Forty-four patients who required subtalar fusion following initial treatment of a displaced intra-articular calcaneal fracture were compared to the population of patients who did not require subtalar fusion. The variables compared between the two groups included Böhler angles, two computed tomography classification systems, and clinical scores including SF-36, visual analogue score, and oral analogue score.

INTERVENTION: Subtalar distraction bone-block arthrodesis with tricortical bone graft was used in all 45 feet.

MAIN OUTCOME MEASUREMENTS: The following were examined: x-ray fracture classification, specifically Böhler angles and Essex-Lopresti classification; computed tomography classification, specifically Sanders and Crosby; clinical scores, specifically validated visual analogue score, general health survey scores, oral analogue score, and other factors (i.e., patient demographics including age, sex, profession, smoking history, and Worker's Compensation Board involvement.

RESULTS: Initial treatment of the 44 patients in our study was nonoperative in 37 (84%) patients and operative (open reduction and internal fixation) in 7 (16%) (1 patient had bilateral heel fractures). Patients requiring fusion differed demographically from those patients not requiring fusion. Mean age was 39 years in both the fusion and nonfusion group. The fusion group had 97% males, whereas the nonfusion group had 89% males. Sixty-four percent of the fusion patients were Worker's Compensation Board claims, whereas 35% of the nonfusion group were Worker's Compensation Board claims. Of those that required fusion, 77% were heavy laborers. On average, the fusion group had a Böhler angle 15 degrees less than the nonfusion group. Forty-six percent of the fusion patients were Sanders-type IV initial fractures. Logistic regression analysis revealed that the primary predictors of requiring fusion were Worker's Compensation Board status (odds ratio = 3.03, 95% confidence interval = 1.41-6.57), Sanders-type IV (odds ratio = 5.48, 95% confidence interval = 1.57-19.18), Böhler angle <0 degrees (odds ratio = 10.64-95% confidence interval = 1.33-85.17), and nonoperative initial treatment (odds ratio = 5.86-95% confidence interval = 2.33-14.67).

CONCLUSION: These data suggest that the amount of initial injury involved with the calcaneal fracture is the primary prognostic determinant of long-term patient outcome. Böhler angle on presentation of <0 degrees was 10 times more likely to require a secondary subtalar fusion than a Böhler angle on presentation of >15 degrees. Sanders-type IV calcaneal fractures were 5.5 times more likely to be fused than a simple Sanders type II fracture. Worker's Compensation Board patients were three times more likely to be fused than non-Worker's Compensation Board patients. Nonoperative care was six times more likely to lead to a late fusion as compared to open reduction and internal fixation treatment. Late fusion provided relief from pain and improved function as evidenced by an improvement in visual analogue score postsurgery. This study demonstrates that there is a distinct patient group with a displaced intra-articular calcaneal fracture who are at high risk of subtalar fusion. These include male Worker's Compensation Board patients who participate in heavy labor work with a fracture pattern with Böhler angle less than 0 degrees. If their initial treatment was nonoperative, the likelihood of requiring late subtalar fusion was significantly increased. Initial open reductional open reduction and internal fixation of patients with displaced intra-articular calcaneal fracture minimized the likelihood that subtalar fusion would be required.