**5. Case presentation**

A 10-year-old boy (football player) suffered bilateral anterior knee pain and consulted a nearby clinic in 2005, but only underwent observational studies. Radiography showed a normal patellar shape on the left, but the lateral edge of the patella seemed deficient on the right. Pain worsened to the point where he could no longer continue playing football. Bilateral bipartite patellae was diagnosed at 12 years old in 2007, and he was introduced to our hospital in October 2007.

Radiography in our hospital revealed bilateral bipartite patellae (Saupe classification, type II) (Saupe, 1943), and showed marked tenderness on the anterolateral aspect of the knees, at the site of dissociated bony fragments (Fig. 8).

Fig. 8. Plain radiography in Case 1. Left figures show the right knee, right figures show the left knee.

Magnetic resonance imaging (MRI) showed signal hyperintensity at the dissociated fragment and fibrous connected site on T2-weighted fat-suppression images.

Lateral retinacular release accompanied by the release of vastus lateralis muscle insertion from the bony fragment were performed on both knees arthroscopically under both intraand extra-articular views using the hanger lifting procedure in November 2007, at 13 years old. At first, conventional arthroscopy was performed to check the cartilage status. The

A 10-year-old boy (football player) suffered bilateral anterior knee pain and consulted a nearby clinic in 2005, but only underwent observational studies. Radiography showed a normal patellar shape on the left, but the lateral edge of the patella seemed deficient on the right. Pain worsened to the point where he could no longer continue playing football. Bilateral bipartite patellae was diagnosed at 12 years old in 2007, and he was introduced to

Radiography in our hospital revealed bilateral bipartite patellae (Saupe classification, type II) (Saupe, 1943), and showed marked tenderness on the anterolateral aspect of the knees, at

Fig. 8. Plain radiography in Case 1. Left figures show the right knee, right figures show the

Magnetic resonance imaging (MRI) showed signal hyperintensity at the dissociated

Lateral retinacular release accompanied by the release of vastus lateralis muscle insertion from the bony fragment were performed on both knees arthroscopically under both intraand extra-articular views using the hanger lifting procedure in November 2007, at 13 years old. At first, conventional arthroscopy was performed to check the cartilage status. The

fragment and fibrous connected site on T2-weighted fat-suppression images.

**5. Case presentation** 

our hospital in October 2007.

left knee.

the site of dissociated bony fragments (Fig. 8).

surface of the cartilage looked almost intact on dissociated sites. We determined the range to release from the shape of the patella from inside the joint, using pierce-marks of 23-G needles for marking. The subcutaneous space was then widely developed. A semi-circular hanger was then applied through the SL access portal by placing the ring-shaped end of the hanger, with the other end of the hanger retracted by hand. Watching the patella and lateral retinaculum from outside the joint, lateral release was able to be performed. The width of release could be checked from both inside and outside the joint (Fig.9).

Fig. 9. Arthroscopic view from inside and outside the joint. A, C) Right knee. B, D) Left knee. A) View from inside the right knee joint, using the AL portal. Black arrow indicates the bipartite patella. No marked cartilage damage was evident. B) View from inside the left knee joint, using the AL portal. C) View from outside the right knee joint, using the SL portal. Lateral release of bipartite patella is successfully completed. The lateral femoral condyle can be seen from outside the joint. D) Lateral release performed under a view from outside the joint. A shaver is introduced from the SL portal. The camera is from the AL portal. The lifting hanger is also seen (white arrow). P, patella. \*Bipartite patellae.

abdominal operations in children (Yokomori et al., 1998), but is also suitable for knee surgery because the diameter is close to that of the patella. Instead of lifting the abdominal wall, we lifted the anterior skin of the knee to achieve extra-articular arthroscopy. The most characteristic feature of this method is the provision of an extra-articular view, which seems effective for these procedures. Views can be obtained from both inside and outside the joint arthroscopically without water. Further, with regard to vastus lateralis release, the benefit of this technique is the ability to keep the joint capsule intact, which is not possible with a conventional intra-articular arthroscopic approach. In terms of MPFL reconstruction, the creation of patellar bone tunnel and tendon passage can be made under arthroscopic view. Both intra- and extra-articular arthroscopic views seem indispensable for precise

The only substantial complication is interstitial edema and subcutaneous adhesion due to developing subcutaneous space. Thus, early mobilization with compression dressing seems

The authors thank Drs. Yasuyuki Fukui, Makoto Nishiyama, Masayuki Ishikawa, Nobuyuki Fujita, and Soraya Nishimura, Mita Hospital, International University of Health and

Bradley DM, Dillingham MF (1998). Bursoscopy of the trochanteric bursa. *Arthroscopy*,

Hashimoto D, Nayeem SA, Kajiwara S, Hoshino T (1993). Abdominal wall lifting with

Klein W (1996). Endoscopy of the deep infrapatellar bursa. *Arthroscopy* Vol.12, No.1, pp. 127-

Kwak JH, Sim JA, Yang SH, Kim SJ, Lee BK, Ki YC (2009). The use of medulloscopy for

Lui TH (2007). Arthroscopically assisted Z-lengthening of extensor hallucis longus tendon.

Maeno S, Hashimoto D, Otani T, Masumoto K, Matsumoto H (2008). Hanger-lifting procedure in knee arthroscopy. *Arthroscopy, Vol.24, No.12*, pp.1426-1429. Maeno S, Hashimoto D, Otani T, Masumoto K, Fukui Y, Nishiyama M, Ishikawa M, Fujita

Nomura E, Inoue M (2003). Surgical technique and rationale for medial patellofemoral

without pneumoperitoneum. *Surg Today*, Vol.23, No.9, pp.786-790.

*Arch Orthop Trauma Surg*, Vol.127, No.9, pp.855-857.

subcutaneous wiring: An experience of 50 cases of laparoscopic cholecystectomy

localized intramedullary lesions: Review of 5 cases. *Arthroscopy, Vol.*25, No.12,

N, Kanagawa H (2010). Medial patellofemoral ligament reconstruction with hanger lifting procedure, *Knee Surg Sports Traumatol Arthrosc*, Vol.18, No.2, pp.157-160. Maeno S, Hashimoto D, Otani T, Masumoto K, Hui C (2010). The "coiling-up procedure": a

novel technique for extra-articular arthroscopy. *Arthroscopy*, Vol.26, No.11, pp.1551-

ligament reconstruction for recurrent patellar dislocation. *Arthroscopy,* Vol.19, No.5,

performance of those methods.

**7. Acknowledgement** 

**8. References** 

131..

1555.

pp.E47

pp.1500-1504.

Welfare, for their excellent technical assistance.

Vol.14, No.8, pp.884-887.

necessary.

The patient began range-of-motion exercises from postoperative day 1, and was able to walk from postoperative day 2. Symptom resolved within 1 month, and radiography showed bone union by 2 months postoperatively in the left knee, and by 4 months in the right knee. Even the inclined bony fragment of the right knee was corrected during the course (Fig. 10).

Fig. 10. Radiography of Case 1 along with time course. A, C, E) Right knee. B, D, F) Left knee. A, B) Radiography at the time of initial complaint of pain in both knees at 11 years old. The shape of the right patella seemed normal (A), but the lateral edge of the left knee seemed deficient (B). C, D) Preoperative radiography at 12 years old. Both knees displayed bipartite patella (Saupe classification, type II). E) Right knee at 4 months postoperatively. F) Left knee at 2 months postoperatively. Bone union seemed complete.
