Patients who had replantation failure needed to undergo at least one additional surgery (including amputation) and had a longer length of hospital stay [4, 15]. These conditions can lead to increased physical, psychosocial, and economic burdens on patients [4, 18]. Exploring risk factors or predictors of replantation failure may have clinical value for replantation management. In this retrospective study of patients with severe traumatic major limb mutilation who had replantation, we found that lactic acid on admission, 72 h cumulative fluid balance, and albumin level taken immediately post-operation, and their joint prediction showed significant predictive power for replantation failure. Moreover, lower limb trauma, MESS, and first 72 h cumulative fluid balance > 4885.6 ml were independently associated with replantation failure.
In this study, the failure rate of replantation was as high as 72.7%, and the delayed amputation rate was 10.6%. These results were similar to those of previous studies, which reported that the amputation rate of blunt arterial trauma of the limbs was 28–71%, and the delayed amputation rate was 11.7% [17, 19]. Higher injury severity, blunt trauma, location of trauma, and absence of pulses may be associated with failure [8]. All the patients were in critical condition in our cohort, almost all of whom had blunt trauma accompanied by discontinuous vessels, nerves, muscles, and bone structures to varying degrees. High energy transfer from blunt injury has been noted to cause extensive damage to associated soft tissue, bone, and nerves [19–21], and this mechanism may be a potential cause of poor outcomes in this cohort.
Major limb mutilation is often accompanied by severe blood loss such that good perfusion is essential for graft survival [22]. Even mild preoperative anemia was associated with an increased risk of wounds, sepsis, and thromboembolic complications in patients undergoing major non-cardiac surgery [23]. Blood loss can result in oxygen delivery (DO2) reduction sufficient to cause tissue ischemia. Lactic acid may be helpful in predicting levels of oxygen debt accumulation and resuscitation needs, and its measurement may serve as a predictor of high-risk trauma [24]. Central venous oxygen saturation as another indicator of tissue oxygenation may be valuable for predicting the prognosis of large limb replantation [25]. Lactic acid and albumin levels were found to be good predictors of replantation failure in this study. The wound healing time of rats in the continuous protein-free diet group was significantly prolonged [26]. Malnutrition is an independent risk factor for infection and wound complications after lumbar fusion and is associated with a longer hospital stay [27]. These common laboratory indicators should be considered during diagnosis and treatment.
Our results showed that the cumulative fluid balance had high sensitivity and good predictive ability. Fluid accumulation may lead to hemodilution, decreased perfusion pressure gradient due to elevated venous pressure, and inhibited oxygen diffusion between capillaries and cells due to interstitial edema [28]. Microcirculatory hypoperfusion and organ ischemia-reperfusion injury are related to prolonged liquid administration time [29]. Reperfusion injury after replantation can lead to irreversible damage, which can activate complement, cytokines, and chemokines, resulting in cell, membrane, and microvascular damage that impairs outcomes [22]. This may partly explain the independent association between excessive fluid involvement and replantation failure.
Restoring tissue perfusion may be critical for successful limb salvage [13]. Of the tissues involved in major limb trauma, muscles are the least resistant to ischemia [30]. Compared with the lower limbs, the upper extremities have less muscle mass, and an increase in collateral circulation may prolong the reperfusion time [31–33]. Anatomic and functional differences make the upper extremities more receptive to limb salvage and/or replantation than the lower limbs [34]. Additionally, the MESS evaluates limb trauma by integrating the extent of bone and soft tissue injury, limb ischemia, shock, and age [4]. Higher MESS increased the risk of delayed amputations. However, despite the high scores, limb salvage was successful in many patients [8]. Although MESS did not have a good sensitivity in predicting replantation failure in this study, it was indeed an independent risk factor. MESS may help quantify the overall severity of limb injury [8]. This highlights the need for MESS evaluation prior to treatment.
Because of the limitations of its retrospective nature, this study could not obtain the details of trauma completely and could not evaluate the recovery of limb function of the patients. In the joint predictive analysis, the cutoff values of each single index could not be obtained. However, these indexes should still be considered in the traumatic mutilation of major limbs. Due to the small sample size, more prospective studies are needed to further analyze the potential predictors.