| Background: High tibial osteotomy is an effective treatment for kneeunicompartmental osteoarthritis, which transferred the knee weight-bearingaxis from the medial joint compartment to the lateral joint compartment, andthus relieve pain, delay the progress of tibiofemoral joint inflammation andcorrective varus. Surgical methods are mainly divided into the lateral closingwedge osteotomy, medial opening wedge osteotomy, dome osteotomy,combined osteotomies. After reviewing the literature of the short-term andlong-term follow-up results of HTO, the overall treatment effect is good. Butthere are a series of complications, in which the patella infera is most common.The incidence of patella infera in the lateral closing wedge osteotomy was89%, medial opening wedge osteotomy had a higher incidence of patellainfera rate than the lateral closing wedge osteotomy. Patella infera causesanterior knee pain, crepitus and limitation of knee motion. The patella inferaaltered patellofemoral congruency and contact stress, which can lead topatellofemoral osteoarthritis eventually. However there is no literature thatanalysis the relation between the change of patellar height and the change ofpatellofemoral joint pressure,and they never analysis the statistical relationshipbetween the patella infra and the patellofemoral joint pressure yet.Purpose: The research developed a patella infra model in a humancadaver, the osteotomy was parallel to the axial plane, and thus uplifted theantero-superior aspect of tibial plateau. The patellar height was measuredunder the four situations: before osteotomy, after the antero-superior aspect oftibial plateau was elevated3.0millimetres, after the antero-superior aspect oftibial plateau was elevated5.0millimetres, after the antero-superior aspect oftibial plateau was elevated10.0millimetres. Also, the pressure applied tolateral and medial patellofemoral cartilage were measured under the four situations when the cadaveric knee specimens were positioned at the flexionangle of30°,60°and90°respectively. It aimed to provide a theoretical basisfor clinic through investing the effect of patella infera on patellofemoralpressure in a human cadaver model.Methods: Six fresh frozen human cadaveric knee specimens (4male,2femal, age ranges from22to51years) were cut20cm from the joint line. Theknee joint specimens were provided by the Third Hospital of Hebei MedicalUniversity. No fractures, knee meniscus and ligament injury, no obviousanatomical deformity of joint and degeneration. any of the knee bone diseaseswas excluded by imaging examination. The knee specimens were thawed over48h before testing. Removal of skin and subcutaneous tissue around the kneejoint, and only keep the bone and ligaments. Measuring the Caton index whenthe knee specimens were positioned at the flexion angle of30°. The kneespecimens were positioned at the flexion angle of30°,60°and90°respectivelyin testing device, and were applied400N of tension forces through thequadriceps. The pressure applied to lateral and medial patellofemoral cartilagewas measured with the Tekscan pressure sensors. An horizontal planeosteotomy of the proximal tibia was performed about2cm above the tibialtubercle and directed to posterior tibia, with the posterior cortical bone notcompletely divided. Gradually opened the bone cut wide using flat chisels andsequentially tapped wooden wedges into the gap to elevate the antero-superioraspect of tibial plateau. The patella infera models were developed by elevatingantero-superior aspect of tibial plateau3.0millimetres,5.0millimetres,10.0millimetres. Two T-type steel plate was mounted to stabilize the osteotomysurfaces. Repeat the above steps. All data were measure3times, the meanvalue was recorded.Results:1The patellar heightThe patellar height decreased significantly with superior elevation ofantero-superior aspect of tibial plateau. The patellar height was evaluatedusing the Caton index. The Caton idex in the knees before osteotomy was 0.95±0.08, which were normal. The Caton idex were reduced to0.92±0.05,0.66±0.04and0.48±0.07respectively after the antero-superior aspect of tibialplateau was elevated3.0millimetres,5.0millimetres and10.0millimetres.2The pressure of the lateral and medial patellofemoral jointBefore osteotomy，the pressure of lateral patellofemoral joint were2.09±0.04,2.14±0.03and1.90±0.03at the flexion angle of30°,60°and90°,and the pressure of medial patellofemoral joint were1.79±0.14,2.03±0.04and1.42±0.13at the flexion angle of30°,60°and90°.After elevating antero-superior aspect of tibial plateau3.0millimetres,the pressure of lateral patellofemoral joint were2.14±0.03,2.25±0.06and1.75±0.06at the flexion angle of30°,60°and90°, and the pressure of medialpatellofemoral joint were2.11±0.02,2.19±0.03and1.23±0.11at the flexionangle of30°,60°and90°.After elevating antero-superior aspect of tibial plateau5.0millimetres,the pressure of lateral patellofemoral joint were2.25±0.06,2.52±0.05and1.67±0.04at the flexion angle of30°,60°and90°，and the pressure of medialpatellofemoral joint were2.19±0.03,2.25±0.04and1.14±0.09at the flexionangle of30°,60°and90°.After elevating antero-superior aspect of tibial plateau10.0millimetres,the pressure of lateral patellofemoral joint were2.52±0.052.67±0.04and1.59±0.03at the flexion angle of30°,60°and90°，and the pressure of medialpatellofemoral joint were2.25±0.04,2.32±0.02and0.96±0.12at the flexionangle of30°,60°and90°.Conclusions: We observed that elevating antero-superior aspect of tibialplateau can lead the patella to move downwards to the femur trochlea. Withthe height of antero-superior aspect of tibial plateau increasing gradually, thepatellar height and the Caton idex were all reduced. After the antero-superior aspect of tibial plateau was elevated3.0millimetres, the Caton idexwas0.92±0.05，the P value was＞0.05. Caton index data show that normalpatellar position was not apparently affected after antero-superior aspect oftibial plateau elevated3.0mm in osteotomy. However，more pressure of lateral and medial patellofemoral joint were caused after the antero-superior aspect oftibial plateau was elevated3.0millimetres,5.0millimetres and10.0millimetres at the flexion angle of30°,60°,90°, the P value were all<0.05. Inconclusion, the pressure of medial and lateral patellofemoral joint weresignificantly increased after osteotomy at the flexion30°to60°. Theseresults prompted us that the pressure of patellofemoral joint were more easilyaffected after high tibial osteotomy. Because there are many limitations in ourtest, nor can we identify such a mechanical change will lead to a degenerationof the articular cartilage. Adequate preoperative evaluation and improvedimaging are required before performing high tibial osteotomy. Theintraoperative operates need be in strict accordance with the preoperativemeasurement, in order to avoid complications. |
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