This study found a significant correlation between the volume of the raised DCIA graft and postoperative use of walking aids and impairment in daily life activities. Moreover, a significant correlation between incision length and neurosensory deficits of the iliohypogastric nerve could be identified. The severity of detected neurosensory deficits correlated with the length of the skin incision: anesthesia of peripheral cutaneous nerves was associated with long skin incisions (280 ± 30.0 mm), whereas patients with hypesthesia and normal neurosensory function had shorter skin incisions (245 ± 10.1 mm and 216 ± 27.7 mm respectively). These results confirm that surgery should be performed as minimally invasive as possible to reduce postoperative donor-site morbidity.
ROM of the hip joint of both legs was investigated during physical examination to quantify the impairment induced by surgery. Flexion and internal rotation were decreased significantly (-10.0° ± 14.9° and − 5.0° ± 5.7 respectively) in comparison to the unaffected leg, while other directions of motion were hardly affected after graft harvesting (Table 2). This shows that raising of DCIA grafts has detrimental effects on mobility of the hip in general and predominantly affects specific motions. As harvesting of the anterior superior iliac spine (ASIS) was frequently performed to obtain an anatomical reconstruction of the mandible (12/15), contraction of muscles originating from the ASIS could cause pain after surgery. Therefore, a significant restriction of flexion and internal rotation may be explained by painful sensations at the ASIS caused by the sartorius and tensor fasciae latae muscle. 33
ANOVA was used to investigate further relations of ROM with patient-specific factors (Table 6). Controversially older patients experienced pronounced impairment in abduction of the operated leg (R = 0.656; p = 0.008), while age and graft volume correlated with smaller deficits in extension (R = (-) 0.53; p = 0.042) and internal rotation, (R = (-) 0,594; p = 0.025). Even though a recent retrospective study reported no significant correlation between age and donor-site morbidity, 34 general physical impairment of the elderly may reasonably explain a more severe impairment after surgery. Nonetheless, there is no reasonable explanation why older patients, or patients who underwent more extensive DCIA graft harvesting should experience fewer postoperative restriction of ROM. The most likely reason for these contentious results may be the weak validity of goniometric measurements and the small sample size of this study. 35
Investigation of muscle strength equally showed that the performed surgery using CAD/CAM impairs functionality on the operated leg. Especially flexion (60% of patients), abduction (40% of patients) and internal rotation (27% of patients) were weaker in comparison to the opposite leg (Table 7). Likewise, low significance of the results may be explained by the low validity of the applied examination technique and its susceptibility depending on the individual perception of the rater. 36,37 There was no significant impact of graft volume on measurements regarding ROM and perceived muscle strength of the leg.
In the last two years, three systematic reviews were published summarizing the findings regarding donor-site morbidity after head and neck reconstruction of the last 20 years 20,28,29. Despite the abundance of existent publications, 21,34,38−50 only few studies are available, which investigate the impact of graft volume on donor-site morbidity after mandibular reconstruction using DCIA grafts 34,51,52. None of them performed physical examinations of patients. In comparison to the average raised bone volume described in literature (15cm3), this study presents a study group with relatively high mean graft volume of 21,17 ± 5,65 cm3. 52
Katz et al. performed a retrospective chart review of DCIA graft patients and could acquire information about the graft volume in 65% of the investigated cases. A mean graft volume of 8.4 ± 6.9 cm3 was found 34. No specifications concerning the applied surgical technique (CAD/CAM vs. conventional surgery) was made. The volume of the bone graft as stated in the reviewed charts was significantly correlated with a longer hospital stay. No correlation of graft volume with functional outcome parameters could be found, due to limited availability of these information by the retrospective study design. This underlines the importance of a post-operative interview and clinical examination, to collect detailed and reliable information. Furthermore, the significance of clinical examinations could be increased, by decrease the influence of the examiner. Valentini et al proposed using electrophysiological measurements to reliably determine the function of peripheral cutaneous nerves 21.
Ghassemi et al. performed a prospective interview with a mixed study group receiving vascular and avascular iliac crest grafts without using CAD/CAM-techniques 51. The correlation between graft volume and postoperative donor-site morbidity was evaluated. Patients with vascularized grafts showed higher graft volumes and were statistically more often exposed to sensible and functional impairment.
As CAD/CAM-techniques have only been part of the clinical routine for ten years, just one other study (Liu et al.) reports of donor-site morbidity in a study population, in which CAD/CAM was used consistently for DCIA graft harvesting. 45 Instead of determining graft volume, Liu et al. collected information about the length of the anterior iliac graft and skin incision to investigate the impact of the invasiveness of the surgery on donor-site morbidity. In contrast to our study, no significant correlations could be identified. As the length of the anterior iliac graft is only measured in one dimension, it does not necessarily correlate with the volume of the graft or the invasiveness of the surgery. Thus, the impact of the examined factors may not be detected properly due to methodological drawbacks.
Investigations regarding neurosensory deficits of the pelvis after conventional iliac crest harvesting have been conducted previously 34,40,44,45,47,49. None of the studies found a significant correlation between incision length and neurosensory abnormalities.
The localizations of nerve alterations most frequently stated in literature (iliohypogastric nerve and cutaneous femoral lateral nerve) are consistent with the findings of this study. 40,44,49 Interestingly, strongly varying frequencies of sensory alterations are reported in literature: While some authors 34 report of only a few patients (2%) and short periods of nerve alterations (< 1 month), others report of a great portion of patients (up to 93%) suffering hyp- or anesthesia in the pelvic region. 40 In this study, nerve impairments were found with an incidence of 53%, which is in the middle range of current literature statings. Findings regarding neurosensory deficits may vary due to the heterogeneity of the existent studies: Depending on the applied surgical technique (mono- vs. bicortical, CAD/CAM vs. conventional, microvascular vs. avascular) and study design (chart review vs. questionnaire vs. clinical examination) postoperative deficits may occur with different frequencies and may be detected with varying reliability. Clinical examinations may exhibit more detailed information about the postoperative function of the hip, than mere retrospective chart review. Finally yet importantly, the time of study conduction may influence postoperative findings, as surgical techniques have improved. 53
In general, the small sample size of this study (n = 15) obliges cautious interpretation of the presented results. Anatomical or functional peculiarities of our specific study group may affect statistical analysis, which is why generalizability of our results remains questionable. Advanced investigations with larger study groups may be necessary to reveal the true effect of DCIA graft harvesting on postoperative impairment of the leg.