The use of open wedge high tibial osteotomy (HTO) to correct varus deformity of the knee is well established. However, the stability of the various implants used in this procedure has not been previously demonstrated. In this study, the two most common types of plates were analysed (1) the Puddu plates that use the dynamic compression plate (DCP) concept, and (2) the Tomofix plate that uses the locking compression plate (LCP) concept. Three dimensional model of the tibia was reconstructed from computed tomography images obtained from the Medical Implant Technology Group datasets. Osteotomy and fixation models were simulated through computational processing. Simulated loading was applied at 60:40 ratios on the medial:lateral aspect during single limb stance. The model was fixed distally in all degrees of freedom. Simulated data generated from the micromotions, displacement and, implant stress were captured. At the prescribed loads, a higher displacement of 3.25 mm was observed for the Puddu plate model (p<0.001). Coincidentally the amount of stresses subjected to this plate, 24.7 MPa, was also significantly lower (p<0.001). There was significant negative correlation (p<0.001) between implant stresses to that of the amount of fracture displacement which signifies a less stable fixation using Puddu plates. In conclusion, this study demonstrates that the Tomofix plate produces superior stability for bony fixation in HTO procedures.
We report on our early experiences with the Press Fit Condylar Rotating Platform (PFC-RP) total knee replacement prosthesis at University Malaya Medical Centre. This new prosthesis was introduced to Malaysia in 2001. It combines the rotating platform technology of Low Contact Stress (LCS) and the modularity of Press Fit Condylar (PFC) system. We performed 18 knee replacements using cruciate retaining prosthesis without patellar resurfacing in 10 patients and followed them up over a period of 16-month. A new operative strategy was developed to match the flexion and extension gaps. The pre- and post-operative assessments were made according to the American Knee Society Scores (AKSS). Post-operative pain relief, range of motion, knee score and functional score showed promising early results. The average knee rating improved from 28 to 91 (range 75-94). Average functional assessment improved from 26 to 82 (range 75-90). The radiographic assessments show correction of an average pre-operative varus of 140 to post-operative valgus of 50 (range 4-70). Early infection occurred in two knees. Both responded to aggressive debridement and antibiotics. Stiffness was encountered in one patient. There were no spinouts of the insert. We are satisfied that the implants are performing well at the one-year mark and will continue monitor this cohort.
This study was carried out to evaluate the long-term effect on the donor side of the foot and ankle following vascularized fibular graft resection in children. Eight patients underwent resection of the fibula for the purpose of a vascularized fibular graft by a surgical team who practiced leaving at least 6 cm residual distal fibula. The age of these children at the time of surgery was between 3 and 12 years. They were reviewed between 3 and 12 years after surgery. Two patients who underwent resection of the middle shaft of the fibula at 3 and 5 years of age developed abnormal growth of the distal tibia, leading to ankle valgus. They were treated with growth modulation of the distal tibial physis and supramalleolar osteotomy with tibiofibular synostosis. Another patient who underwent the entire proximal fibula resection at the age of 6 years had developed hindfoot valgus because of weakness of the tibialis posterior muscle. He required talonavicular fusion and flexor hallucis to tibialis posterior muscle transfer. Patients operated at the age of older than 8 years neither had ankle nor hindfoot deformity. We concluded that resection of the middle shaft of the fibula for the purpose of a vascularized fibula graft, leaving a 6 cm distal fibular stump in children younger than 6 years old, may give rise to abnormal growth of the distal tibial physis, leading to valgus ankle. The entire proximal fibular resection for the similar purpose in a 6-year-old child may give rise to weakness of tibialis posterior and hindfoot valgus.