What Factors Are Associated With Failure of Compressive Osseointegration Fixation?

BACKGROUND: Compressive osseointegration is as an alternative to traditional intramedullary fixation. Two- to 10-year survivorship and modes of failure have been reported; however, as a result of relatively small numbers, these studies are limited in their ability to identify risk factors for failure. QUESTIONS/PURPOSES: (1) What is survivorship free from aseptic mechanical and survivorship free from overall failure of compressive osseointegration fixation? (2) What patient factors (age, sex, body mass index [BMI], anatomic location of reconstruction, indication for reconstruction, radiation, chemotherapy) are associated with increased risk of failure? METHODS: Between 2006 and 2014, surgeons at one center treated 116 patients with 137 Compress® implants for lower extremity oncologic reconstructions, revision arthroplasty, and fracture nonunion or malunion. One hundred sixteen implants were available for review with a minimum of 2-year followup (mean, 4 years; range, 2-9 years). Kaplan-Meier survival plots were produced to examine survivorship and Cox regression modeling was used to generate hazard ratios (HRs) for potential risk factors for failure. Patient factors (age, sex, BMI, anatomic location of reconstruction, indication for reconstruction, radiation, chemotherapy) were obtained from chart review and an institutional database. RESULTS: Survivorship free from aseptic mechanical failure was 95% (95% confidence interval [CI], 91%-99%) at 18 months and 93% (95% CI, 86%-99%) at 4 years. Survivorship free from overall failure was 82% (95% CI, 75%-89%) at 18 months and 75% (95% CI, 66%-84%) at 4 years. Risk of overall failure was increased with reconstruction of the proximal tibia (HR, 4.42; 95% CI 0.98-19.9) and distal femur (HR, 1.74; 95% CI, 0.50-6.09) compared to the proximal femur (HR, 1; referent; p = 0.049). Risk of aseptic mechanical failure was increased with reconstruction of the proximal tibia (HR, 1; referent) and distal femur (HR, 0.37; 95% CI, 0.08-1.77) compared with the proximal femur (HR, 0, p = 0.048). Radiation was associated with increased risk of overall failure (HR, 3.85; 95% CI, 1.84-8.02; p < 0.003), but not aseptic mechanical failure. Age, sex, BMI, chemotherapy, and surgical indication were not associated with increased risk of aseptic or overall failure. CONCLUSIONS: This study questions the use of age as a contraindication for the use of this technology and suggests this technology may be considered in proximal femoral reconstruction and for patients with indications other than primary oncologic reconstructions. Future research should establish long-term survivorship data to compare this approach with conventional intramedullary stems and to evaluate the potential benefits of preventing stress shielding and preserving bone stock in revision situations. LEVEL OF EVIDENCE: Level III, therapeutic study.

Calcaneal tuberosity fractures through prior Schantz pin sites in patients with diabetic neuropathy.

Schantz pin placement in the calcaneal tuberosity is a common procedure known to be complicated by pin site infections and nerve injuries. Fractures through Schantz pin sites has been reported mostly in diaphyseal bone. This case series highlights three patients with type 2 diabetes mellitus and diabetic neuropathy who were fixed in an external fixator frame with a pin through the calcaneal tuberosity. At an average of 13 weeks, the patients presented with fracture through the pin site at the calcaneal tuberosity. One patient was treated with open reduction and internal fixation of the calcaneus and two patients were treated nonoperatively. These cases suggest that placement of calcaneal pins in patients with diabetic neuropathy harbors risk of iatrogenic fracture, a complication that has not been reported in the literature.