Effects of rotating-knee system versus hinge-knee system replacement in knee salvage of tumor

Shide LI; Xinglin ZHANG

ABSTRACT

BACKGROUND:

With the development of n0eo-adjuvant chemotherapy, 5-year survival rate of bone tumors has significantly increased. Limb salvage has replaced amputation to become a major means of treating knee tumors and has achieved good results.

OBJECTIVE:

To investigate and compare the effect of knee joint reconstruction using hinge-knee system and rotating knee system. DESIGN, TIME AND

SETTING:

Comparative observation. The patients were selected from Department of Spine and Orthopedic Surgery, First Affiliated Hospital of Gaungxi Medical University between June 1999 and March 2006.

PARTICIPANTS:

A total of 72 patients with tumor round the knee were selected from the First Affiliated Hospital of Gaungxi Medical University, and 9 cases were lost in follow-up. Of the remaining 63 cases, there were 35 males and 28 females, aged 31 years (range, 15-58 years); 40 cases underwent knee joint reconstruction using hinge-knee system and 23 using rotating knee system.

METHODS:

The tumor excision of superior tibia was performed according to Ennecking principle. After joint reduction of hinge-knee prosthesis, the bolt was adjusted and locked; the high polymer polyethylene pad was placed in rotating knee system, and the joint rotation axis was assembled. The tumor excision of inferior tibia was performed from the medial thigh along medial vastus muscle posterior margin till medial patellar ligament of superior tibia. After joint reduction of hinge-knee prosthesis, the bolt was adjusted and locked; the high polymer polyethylene pad was placed in rotating knee system, and the joint rotation axis was assembled. MAIN OUTCOME

MEASURES:

The treatment effect was evaluated according to MSTS functional scores, ambulation scores, flexion-extension-angle, knee rotation and infection, relapse and operative time.

RESULTS:

The 63 patients were followed up for 9 months to 8 years. In hinge-knee system group, operative time was (2.663±0.336) hours; there were 5 cases of relapse, 3 cases of metastasis/death and 2 case of infection. In rotating knee system group, operative time was (2.572±0.288) hours; there were 3 cases of relapse, 2 cases of metastasis/death, and 2 case of infection. One case in rotating knee system group developed fracture and dislocation of the polyethylene bush of rotating axis and there was no syndrome after changing fittings. No prosthesis loosening was found in two groups. With exception of patients with relapse and metastasis/death, 50 cases were evaluated, and no significant difference was found in MSTS scores between two groups (P > 0.05); the total score and single item score of ambulation scores in rotating knee system group were significantly greater than hinge-knee system group (P < 0.05). The extension angle in two groups reached or was close to 0°, and the flexion-extension angle of hinge-knee system group (119.375±17.490)° was similar to rotating knee system group (125.000±15.340)° (P=0.260).

CONCLUSION:

The rotating knee system displays superior function than hinge-knee system in knee salvage after surgery. Ambulation scores revealed that the knee joint function of the rotating knee system is superior over hinge-knee system, while the MSTS scores did not. Therefore, ambulation scores is more sensitive and appropriate to evaluate the function after knee salvage. There were no significant differences in operative time and flexion-extension ability and syndrome between two methods.