The purpose of this study is to elucidate the possibility of an ideal joint alignment after monofocal lengthening of tibia in achondroplastic patients. In 10 cases of the alignments of knee and ankle joints of tibias in which plane radiographs were examined.Unilateral fixators were applied to both tibias,after lengthening in the normal manner, deformity was corrected manually in a single procedure without anesthesia. In order to determine the amount of angle to be corrected, a line was first drawn on the radiograph from the center of the knee joint to the center of the ankle joint. (This line is named the Knee-ankle line: KAL).

Next we drew a line along the ankle joint and measured the angle between this line and KAL. We also drew a line across the tibial plateau and measured the medial angle between this line and KAL. We tried to align the ankle joint perpendicular to KAL and the medial angle between the tibial plateau and KAL at 87 degrees , instead of trying to align the axis of the tibial shaft perfectly straight. The medial angles between the line across the tibial plateau and KAL were corrected to 86 degrees in average, with a range from 84 to 90 degrees, and the medial angles between the line across the ankle joints were corrected to 87 degrees in average, ranging from 80 to 90 degrees in result.

In conclusion, joint alignments of tibias in achondro-plastic patients were able to be corrected successfully without any complications using our monofocal lengthening technique. And severe varus deformities of tibias can be corrected even with monofocal lengthening technique by trying to correct the alignments of knee and ankle joints rather than trying to straighten tibial shafts.

Tartrate-resistant acid phosphatase is contained in multinucleated giant cells of giant cell tumour of bone (GCT) and chondroblastoma (CBL) as well as in osteo-clasts. Yet few studies have so far been done regarding serum acid phosphatase (AcP) level in patients of GCT or CBL. The purpose of this study is to elucidate the clinical significance of serum AcP as a tumour marker for GCT and CBL. Serum AcP value was examined in nine GCT patients and three CBL patients before and after surgery. In the GCT cases, serum AcP values before surgery were high in five cases. They were 14.0 IU/L, 68.7 IU/L, 45.9 IU/L, 21.9 and 31.3 IU/L (normal value; 7.1–12.6 IU/L). They decreased after surgery to 7.7 IU/L (55% of the preoperative value), 8.2 IU/L (12%), 7.8 IU/L (17%), 6.1 IU/L (28%) and 10.0 IU/L (32%), respectively. Serum AcP values before surgery were within normal limits in the remaining four GCT cases. Even in these four cases, postoperative serum AcP level was lower than the preoperative level. Postoperative/preoperative AcP ratios in these four cases were 67%, 80%, 69% and 76%. In the CBL cases, serum AcP values were high in all cases. They were 15.1 IU/L, 13.1 IU/L and 13.7 IU/L. They decreased after surgery to 10.3 IU/L (68% of the pre-operative value), 10.2 IU/L (78%) and 9.7 IU/L (71%), respectively, all within normal limits. Therefore, it is concluded that serum AcP is a useful tumour marker for GCT and CBL in diagnosing the tumour as well as in evaluating the efficacy of treatment.