Table 3.
Associations of patient and procedural characteristics with success versus failure of medial gastrocnemius flap (bivariate analysis)
| Characteristic | Mean for successful treatment* | Mean for failed treatment* | Number of failures (percent) | p Value† |
|---|---|---|---|---|
| Age (years) | 61 ± 16 | 62 ± 11 | n/a | 0.950 |
| Sex | 0.476 | |||
| Female (n =12) | n/a | n/a | 5 (42%) | |
| Male (n =15) | n/a | n/a | 9 (60%) | |
| BMI (kg/m2) | 35 ± 8 | 33 ± 7 | n/a | 0.326 |
| Charlson comorbidity index | 1.4 ± 1.5 | 1.4 ± 1.3 | n/a | 0.826 |
| Diabetes mellitus | 0.786 | |||
| No (n = 22) | n/a | n/a | 12 (55%) | |
| Yes (n = 5) | n/a | n/a | 2 (40%) | |
| Smoker | 0.853 | |||
| No (n = 25) | n/a | n/a | 13 (52%) | |
| Yes (n = 2) | n/a | n/a | 1 (50%) | |
| Coronary artery disease | 0.382 | |||
| No (n = 21) | n/a | n/a | 12 (57%) | |
| Yes (n = 6) | n/a | n/a | 2 (33%) | |
| Number of knee arthrotomies before flap | 3.7 ± 2.4 | 4.3 ± 2.8 | n/a | 0.354 |
| Prior extensor mechanism disruption | 0.361 | |||
| No (n = 21) | n/a | n/a | 9 (43%) | |
| Yes (n = 6) | n/a | n/a | 5 (83%) | |
| Prior completed two-stage revision | 0.313 | |||
| No (n = 22) | n/a | n/a | 11 (50%) | |
| Yes (n = 5) | n/a | n/a | 3 (60%) | |
| Defect area (cm2) | 28 ± 25 | 14 ± 6 | n/a | 0.197 |
| Surgical service performing flap | 0.575 | |||
| Plastic surgery (n = 8) | n/a | n/a | 5 (63%) | |
| Orthopaedics (n = 19) | n/a | n/a | 9 (47%) | |
| Knee procedure at time of flap | 0.033 | |||
| Irrigation and débridement or TKA prosthesis replantation (n = 13) | n/a | n/a | 4 (31%) | |
| Spacer placement/exchange (n = 14) | n/a | n/a | 10 (71%) | |
| Type of spacer if flap part of two-stage | 0.261 | |||
| None/TKA irrigation and débridement (n = 5) | n/a | n/a | 1 (20%) | |
| Static (n = 12) | n/a | n/a | 8 (67%) | |
| Articulating (n = 10) | n/a | n/a | 5 (50%) | |
| Growth of Staphyloccus aureus | 0.721 | |||
| No (n = 14) | n/a | n/a | 7 (50%) | |
| Yes (n = 13) | n/a | n/a | 7 (54%) | |
| Growth of Enterococcus | 0.749 | |||
| No (n = 23) | n/a | n/a | 12 (52%) | |
| Yes (n = 4) | n/a | n/a | 2 (50%) | |
| Growth of Gram-negative rods | 0.911 | |||
| No (n = 20) | n/a | n/a | 11 (55%) | |
| Yes (n = 7) | n/a | n/a | 3 (43%) | |
| Growth of resistant bacteria (MRSA/VRE) | 0.235 | |||
| No (n = 19) | n/a | n/a | 9 (47%) | |
| Yes (n = 8) | n/a | n/a | 5 (63%) | |
| Polymicrobial growth | 0.270 | |||
| No (n = 19) | n/a | n/a | 9 (47%) | |
| Yes (n = 8) | n/a | n/a | 5 (63%) |
* Mean ± SD; †p values are from Cox proportional hazards survival analysis models. A Bonferroni correction was applied owing to the large number of univariate statistical tests; 19 tests were performed, requiring that the level of significance be lowered from 0.05 to 0.004, therefore no p value in this table was considered to be statistically significant; n/a = not applicable; MRSA = methicillin-resistant Staphylococcus aureus; VRE = vancomycin-resistant Enterococcus.