Aim

Diagnosing periprosthetic joint infection after total joint arthroplasty is often challenging. The alpha defensin test has been recently reported as a promising diagnostic test for periprosthetic joint infection. The goal of this study was to determine the diagnostic accuracy of alpha defensin testing.

Our aim was to accurately determine whether muscle atrophy and fatty infiltration are reversible following cuff repair. Patients with a repairable cuff-tear were recruited and assessed clinically and radiologically (Magnetic Resonance Imaging). At surgery, supraspinatus was biopsied. Post-operatively, patients underwent clinical evaluation at standardised intervals, with further MRI and an ultrasound guided biopsy of supraspinatus at 12 months.

MRI was used to characterize cuff-tears and determine the degree of muscle atrophy and fatty infiltration. Biopsy samples were fixed on-site and transported for processing. Morphometric assessments of myofibres were made and mean cross-sectional areas calculated using validated techniques. The pathologist was blinded to sample details. Statistical analysis was performed to assess differences in mean myofibre area following cuff repair and correlated with radiological findings.

Eight patients were available for completed histological and radiological analysis. Six (two re-tears) demonstrated sizeable and highly statistically significant improvements in mean myofibre cross-sectional area (P=0.000–0.0253). Of the two not showing any increase in myofibre area, neither result was statistically significant (P=0.06, 0.2); one was a re-tear and one was a repair of a partial-thickness tear. Radiologically, the muscle and fatty changes had not demonstrably changed.

Our finding that myofibre cross-sectional area increases following cuff repair suggests muscle atrophy is a potentially reversible process. Even with re-tears, improvements were seen. MRI features of fatty infiltration and muscle atrophy were not seen to improve however. It is likely that radiological assessment is not sensitive enough to demonstrate the reversibility of muscle atrophy seen on histological analysis at one year.

Taylor Spatial Frame (TSF) is a six axis deformity correction frame and accuracy of correction depend on the accuracy of parameters input in to the web based software. There are various methods of obtaining frame and deformity parameters (13 in total) including the use of dedicated software known as SpatialCAD™. We tested the accuracy of SpatialCAD™ using a saw bone two ring frame construct of known parameters. We mounted a two-ring (155mm) frame on a saw bone tibia and fibula unit and worked out the accurate mounting and deformity parameters. Then we obtained orthogonal and nonorthogonal antero-posterior and lateral images of frame using a metallic sphere of known dimensions placed at the level of the bone, to aid calibration of x-ray images. We also obtained orthogonal and non-orthogonal images without a calibrating sphere. We then uploaded the images in to SpatialCAD™ software and obtained the mounting and deformity parameters and compared with the real parameters. SpatialCAD™ is capable of yielding measurements within 1–2mm of actual measurements when Calibrated orthogonal images were used. The software was inaccurate when frame hardware of known dimensions was used for calibration because the hardware was not in the same plane as the bone

Limb lengthening with external fixators has many complications, like pin track infection, joint stiffness, severe pain and stress fracture after removal of external fixator. Prolonged period in external fixator interferes with rehabilitation and activities of daily living.

We describe our results with ISKD (intramedullary skeletal kinetic distractor) system, an internal limb lengthening device, activated with rotations of 3 degrees. In this retrospective cohort we performed lengthening with the use of ISKD in 12 patients from March 2006 to date. Ten patients were included in this study as two patients had not completed the stage of consolidation. There were 7 male and 3 female patients. Their average age was 44 years (range 23–63). The mean follow up period was 16 months (range 12–24 months). Two patients had tibial lengthening and eight patients had femoral lengthening. The average lengthening desired was 42.5 mm (range 2.5 mm–75 mm). The average lengthening achieved was 38 mm. Mean hospital stay was 7 days (range 5–11 days). The distraction index was 1.2 mm/day. The average time to full weight bearing was 6 months (range 4 to 10 months). Mean healing time was 10.25 months. The mean healing index was 90.7 days/cm. If we remove two patients who took long time to heal, the mean healing index drops to 61 days/cm. Two patients needed bone grafting at the distraction site. None of the patients had infection, non-union of the distraction site or breakage of the nail. None of the patients had joint stiffness. All patients were completely satisfied with the treatment and had excellent functional results. We conclude that the low rate of complications, higher patient acceptability and avoidance of external fixation make ISKD a very attractive option for limb lengthening.