2015 ISAKOS Biennial Congress ePoster #1911

Longitudinal Change of Medial and Lateral Patellar Stiffness After Reconstruction of the Medical Patellofemoral Ligament in Patients with Recurrent Patellar Dislocation

Nobuyuki Kumahashi, MD, PhD, Izumo, Shimane JAPAN
Suguru Kuwata, MD, PhD, Hamada, Shimane JAPAN
Masanori Egusa, PhD, Izumo JAPAN
Taku Tadenuma, MD, Izumo, Shimane JAPAN
Hiroshi Takuwa, MD, Izumo, Shimane JAPAN
Masaru Kadowaki, MD, Izumo, Shimane JAPAN
Yuji Uchio, MD, PhD, Izumo, Shimane JAPAN
Department of Orthopaedics, Izumo, Shimane Prefecture, JAPAN

FDA Status Not Applicable

Summary: This study demonstrates that the medial and lateral stiffness of patella at knee full extension evaluated with the new patellar apparatus were well-balanced six months after MPFL reconstruction and maintained the balance up to two years following surgery, with good clinical results.

Abstract:

Background

The patients with recurrent patellar dislocation feel apprehension around the knee full knee extension. However, there has been no convenient instrument for patellar instability at knee full extension. The serial change of stiffness of the medial and lateral patellar ligament after reconstruction of the medial patellofemoral ligament (MPFL) on recurrent patellar dislocation at full knee extension is also unknown.

Purpose

To clarify the change of the medial and lateral stiffness of the patellar ligament at full extension before and after MPFL reconstruction for 2 years with the new patellar apparatus.

Methods

Sixteen consecutive patients (18 knees from 3 men and 13 women; mean age, 22 years; range, 16-38 years) and 28 heathy knee reference subjects (mean age, 28) were included in this prospective study. The subjects were followed for 24 -77 months. The stiffness of the medial and lateral patellar ligament was measured in both groups at 0 degree of knee extension with a patella stability tester before surgery and 3, 6, 12, 18, and 24 months after MPFL reconstruction. The MPFL reconstruction in single patellar and femoral bone tunnels was performed using the semitendinosus tendon with and without lateral release, depending on the preoperative lateral patellar stiffness and it was fixed with an interference screw system at 30 degree of knee flexion under 10 N lateral force. A knee brace with a 30 degree extension limit was placed for three months post-operatively not to stretch the graft. ROM exercise and partial weight-bearing were started one week after surgery, and full weight-bearing was permitted at 4 weeks. The knee brace was removed 3 months postoperatively and jogging started at the same time. Six months postoperatively, the patient was allowed to return to full sports. The apprehension test, range of motion, plain X-ray measurements (tilting angle, congruence angle and lateral shift ratio), and Kujala score, also were examined before and after surgery.

Results

The medial and lateral stiffness of affected knees before and after surgery in patient group were significantly lower than that of the healthy knees from the reference subjects (P<0.05). The medial stiffness, not the lateral one, of the operated side after surgery was significantly elevated compared to its preoperative stiffness and to the contralateral sides (P<0.05). This elevation was maintained for two years. Furthermore, medial stiffness was significantly higher than that of lateral one at three months after operation. Medial and lateral stiffness were well-balanced after six months and lasted up to two years postoperatively. The range of motion after operation was not limited in all cases. The apprehension test was all positive before operation and all negative except one case after operation. The postoperative X-ray findings and clinical scores were significantly improved during the follow-up period (P<0.05), and no recurrent dislocation was observed.

Conclusions

The medial stiffness of the patella after operation was significantly elevated compared to the preoperative and contralateral ones and this elevation lasted up to two years. The medial and lateral stiffness were well-balanced six months after MPFL reconstruction, and maintained the balance up to two years following surgery, with good clinical results.