2.2. Operative technique and rehabilitation protocol

Under anesthesia, the patella and patellar tendon were exposed through a mid-axial longitudinal approach. The fracture lines were irrigated and cleared of blood clots and small debris to allow exact reconstruction. Afterwards, insert the Krackow stitch of #5 non-absorbable suture into each side of the patellar tendon bilateral symmetrically, as illustrated (Fig. ​(Fig.1A1A and B). Then 3 longitudinal drill holes in the proximal patellar fragment were made and the free ends of the sutures were pulled through the holes ready to tighten. Likewise, a horizontal drill hole at the proximal pole of the patella vertical to the former three holes was made beforehand for cerclage. Next, fragment reduction was monitored, and a cerclage wire (figure-of-zero) was passed through the horizontal hole around the patella (Fig. ​(Fig.2A).2A). The wire was then twisted and tightened to maintain the reduction. The sutures were then tightened and tied deep to the quadriceps tendon, with the knee in full extension (Fig. ​(Fig.2B).2B). Finally, retinacular tears were repaired and the wound was closed.

Schematic drawing describes the hybrid technique: cerclage wiring around patella with transosseous tunnels suture (A and B). When knee bending, the tensions exerted on the distal avulsion fragments of patella are shown as vectors in (C). The resultant force is directed vertically to the coronal plane of patella, which gives rise to the fracture gap.

Intraoperative view: Krackow sutures through the transosseous patellar drill tunnels and the cerclage wire before twisting (A); The avulsion fragments was reduced after the cerclage wire and Krackow sutures were frapped (B).

After the surgery, static isometric quadriceps exercises were started on the first day postoperatively; then the program of straight leg raise and active flexion exercises were initiated on the fifth day or earlier as long as pain Visual Analogue Scale was lower than 4. Rehabilitation program continued until full range of knee motion was restored.