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.

In this retrospective study postoperative subscapularis (SSC) function was measured with an electronic force measurement plate (FMP) and clinical scores and correlated with SSC-muscle cross sectional area on defined MRI-sequences.

82 patients with subscapularis tears (34 isolated SSC tears and 48 combined SSC/SSP tears) were followed up at a mean of 38 (24–72) months after tendon reconstruction with the Constant score (CS) and clinical SSC-tests (Napoleon test, Lift off test). SSC-muscle function was assessed in the belly-press- and the lift off position using a custom made electronic FMP (force in Newton). SSC muscle strength values were compared with the contra-lateral side. SSC-muscle atrophy (muscle cross sectional area in mm²) was measured on standardised sagittal MRI-planes and compared with a healthy matched control group (CG) (Mann-Whitney-U-Test).

The mean CS improved from 51p to 81p in isolated tears (group 1) and from an average 47 p to 78 p in combined tears (group 2) (each p< 0.01). Overall 85% of the patients rated their result as good or excellent. Positive and intermediate postop. Napoleon tests were still present in 30% in group 1 and in 25% in group 2. Mean postoperative SSC-muscle strength in the belly-press position averaged 64 N (contralatera sidel-CL: 86 N) in group 1 and 81 N (CL: 91 N) in group 2. Lift-off test strength averaged 36 N (CL: 69 N) in group 1 and 50 N (CL: 63 N) in group 2 (each p< 0.05). Postoperative MRI revealed a significant reduced SSC muscle cross sectional area for the operated side compared with the CG (group 1: SSC: 1974 mm²; CG 2980 mm² p< 0,05; group 2: SSC: 1829 mm²; CG 2406 mm² − SSP: 570 mm²; CG 812 mm² each p< 0,05).

Despite good clinical results after reconstruction of isolated and combined subscapularis tears a marked subscapularis strength deficit remains that is not reflected in the Constant Score, but can be detected with the new measurement device. Additionally a subscapularis muscle atrophy remains in the postoperative course that cannot be reversed by surgery.