To characterize the quality of flap tissues and the resident cells in order to provide a scientific rationale for reattaching flap tissues during surgery. 11 acetabular chondral flaps and 3 non-delaminated cartilage samples were resected during open hip surgeries and the anatomical orientation was marked. The viability was measured in 7 flaps with Live Dead staining and the distribution of the extracellular matrix components was investigated in 7 oriented flaps by histology. The chondrogenic potential of the residing cells (P2) was investigated via pellets assays (5 flaps). Their capacity to outgrow from flap particles was tested upon encapsulation in 4mm-diameter fibrin glue discs (6 flaps). The viability in flaps was 49.4 ± 6.5 % compared to 70.6 ± 8.2 % in non-delaminated cartilage, (not significant). Histology showed a progression of fibrillation from the delaminated side towards the site of attachment. This degraded state correlated with the capacity of the cells to outgrow, with 60.6 ± 33 % of the gel area covered by migrating cells after 4 weeks in culture. However, the cells in flaps showed a decreased chondrogenic potential than chondrocytes from non-delaminated cartilage. Our findings indicate that flaps contain viable cells that can outgrow from the tissue due to the degraded state of the matrix. The poor chondrogenic property of the cells suggests they are unlikely to produce enough matrix to provide a solid attachment of the delaminated tissue upon migration.
The classical longitudinal incision used for the direct anterior approach (DAA) does not follow the relaxation tension lines of the skin and can lead to impaired wound healing and poor scar cosmesis. The purpose of this study was to determine patient functional and radiographic outcomes of a modified skin crease “bikini” incision used for the DAA in THR. 964 patients (51% female; 59% longitudinal, 41% bikini) completed 2 to 4 years after surgery a follow-up questionnaire including the Oxford Hip Score (OHS), the University of North Carolina 4P scar scale (UNC4P), and two items for assessing aesthetic appearance and symptoms of numbness. Implant position, rates of radiographic heterotopic ossification and required revision were assessed. UNC4P total (p<0.001) and OHS (p=0.013) scores were better in the bikini compared the longitudinal group. The proportion of aesthetically very satisfied patients was higher (p<0.001) in the bikini group. The proportion of patients reporting numbness in the scar was higher (p<0.001) in the longitudinal (14.5% versus 7.5%, respectively). Radiographic cup abduction angles, stem position and ectopic ossification rates did not differ between the groups. No differences in the revision rates of both groups being 2.1% in the longitudinal and 1.5% in the Bikini group. Although differences were not huge, Bikini incision resulted in better patient-related outcomes and satisfaction related to the scar. Our study showed that a short oblique “bikini” skin crease incision for the DAA can be performed safely without compromising implant positioning or increasing symptoms suggesting lateral femoral cutaneous nerve dysesthesia. As it is less extensile it should be used after having gained significant experience with the classic longitudinal incision.
