American Academy of Orthopaedic Surgeons Annual Meeting

American Academy of Orthopaedic Surgeons Annual Meeting

Issue: May 2011
May 01, 2011
3 min read

Study finds 47% primary union rate in tibia patients with ‘critical-sized’ bone defects

The findings indicate one definition for a critical defect may be an overestimation.

Issue: May 2011
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Discuss in OrthoMind
Discuss in OrthoMind

Using a fracture gap at least 1 cm in length involving more than 50% of the cortical diameter as a definition for a critical-sized defect of the tibia does not ensure reoperation rate, according to a recently presented study.

David Sanders, MD, shared his group’s findings at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.

“The management of traumatic bone defects is controversial,” Sanders said. “Two primary strategies are to just watch and wait vs. doing some type of bone grafting or other procedure on an immediate basis. The difficult in interpreting previous studies is the natural history is unknown — as well as the clinical significance.”

Combing through the SPRINT trial

Sanders and his group investigated the 1,225-patient SPRINT trial for literature involving critical defects. They defined a critical defect as one that was not expected to heal in the absence of secondary intervention. Using a definition of critical defects involving more than 50% of the cortical diameter of the tibia and being greater than 1 cm in length, the group set out to “ascertain the significance of these critical-sized defects in terms of the rate of secondary surgery, which factors are associated with non-union and the overall outcome of the patients involved,” Sanders said.

David Sanders, MD
David Sanders

Patients in the study were evaluated for secondary interventions to gain union such as bone grafting, bone transport and implant exchange.

“We also made a strict definition for planned vs. unplanned surgery,” Sanders said. “Planned being something performed according to institutional protocol at the time of initial injury vs. unplanned surgery being something performed to correct the non-union once it occurred.”

The group compared patients with bone defects to those in the overall SPRINT cohort, then looked within the bone defect cohort to compare those who had a reoperation vs. those who did not. Both comparisons, Sanders said, included issues relating to patient demographics, fracture characteristics, surgical factors, and 1-year function.

Results and findings

“Of the 1,225 patients in the trial, only 37 had a critical-sized defect,” Sanders reported. “Of these, seven had a planned reoperation according to institutional protocol.”

Sanders also reported that of the remaining 30 patients, 14 healed primarily without the need for reoperation, “suggesting there is an overall 47% primary union rate on these patients with so-called critical-sized defects.”

Reoperations included bone grafts, implant exchanges, fracture site debridements, occasional shortening and synostosis procedures. Patients with a defect had worse overall functional outcomes — displaying SF-36 scores around five points lower on average.

Within the cohort of patients with a bone defect, comparing those who had no reoperation with those who required a reoperation revealed patients were less likely to require a reoperation to gain union if they were female or if a reamed nail was utilized at the time of the index procedure.

“Patients with a reamed nail had a 64% primary union rate compared with a 26% in the unreamed group,” Sanders said.

Size not necessarily critical

Sanders said it is important to note that the definition of a critical-sized defect used within this study did not ensure reoperation and added that further research is warranted.

These bone defects “are obviously clinically important, with lower rates of union compared to tibial fractures without defects — and worse functional outcomes compared to the overall cohort,” he concluded. “However, defining a critical-sized bone defect as a 1-cm longitudinal defect involving 50% or greater of the cortical diameter might be overestimating things a bit. We had a primary union rate of 47%, suggesting this size defect is not necessarily critical.” — by Robert Press

  • Sanders D, Swiontkowski MF. The critical sized defect in the tibia: Is it critical? Results from the SPRINT trial. Paper #382. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.

  • David Sanders, MD, can be reached at the London Health Sciences Centre, London, Ontario, Canada N6A 465; email:
  • Disclosure: Sanders is a paid consultant for Smith & Nephew and receives research or institutional support from Smith & Nephew and Synthes.


This is an important article as it emphasizes the need to be patient with tibial defects with 50% of cortical loss and defect length of 1 cm or greater. There has been a move to perform reoperations early (as early as 3 months) in delayed unions, as many surgeons felt they can predict a bad outcome at 3 to 6 months. This article clearly illustrates a wait of 6 to 9 months may be more appropriate as long as the patient’s symptoms are not increasing. This level 1 evidence would indicate we could avoid surgery on 50% of the patients in the group and 64% of a subset of patients who had received a reamed locked nail.

One of the more promising findings is that the response to later intervention remained high when performed with an exchange nail. The savings to the patient and the health care system are obvious.

— Ross K. Leighton, MD, FRCS
Queen Elizabeth II Health Sciences Centre
Division of Orthopaedic Surgery
Halifax, NS, Canada