Preoperative Measurement of Tibial Resection in Total Knee Arthroplasty Improves Accuracy of Postoperative Limb Alignment Restoration

Background：Accuracy of implant placement in total knee arthroplasty （TKA） is crucial.Traditional extramedullary alignment instruments are fairly effective for achieving the desired mean tibial component coronal alignment.We modified the traditional tibial plateau resection technique and evaluated its effect on alignment restoration.Methods：Two hundred and eighty-two primary TKAs in our hospital between January 2013 and December 2014 were enrolled in this retrospective study.Group A consisted of 128 primary TKAs performed by one senior surgeon.Preoperative measurement of the tibial resection was conducted on radiographs,and the measured thicknesses of the lateral and medial plateau resection were used to place the tibial alignment guide.Group B consisted of 154 primary TKAs performed by the other senior surgeon,using a traditional tibial plateau resection technique.In all patients,an extramedullary guide was used for tibial resection,and preoperative and postoperative full-leg standing radiographs were used to assess the hip-knee-ankle angle （HKA）,femoral component alignment angle （FA）,and tibial component alignment angle （TA）.A deviation ≥3° was considered unsatisfactory.Data were analyzed by unpaired Student＇s t-test.Results：The mean postoperative H KA and TA angles were significantly different between Groups A and B （178.2 ± 3.2° vs.177.0 ± 3.0°,t =2.54,P =0.01;89.3 ± 1.8° vs.88.3 ± 2.0°,t =3.75,P =0.00,respectively）.The mean postoperative FA was 88.9 ± 2.5° in Group A and 88.9 ± 2.6° in Group B,and no significant difference was detected （t =0.10,P =0.92）.There were 90 （70.3%） limbs with restoration of the mechanical axis to within 3° of neutral alignment and 38 （29.7%） outliers （〉3° deviation） in Group A,whereas there were 89 （57.8%） limbs with restoration of the mechanical axis to within 3° of neutral alignment and 65 （42.2%） outliers （〉3° deviation） in Group B.The severity of the preoperative alignment deformity was a strong predictor for postoperative alignment.Conclusions：Using conventional surgical instruments,preoperative measurement of resection thickness of the tibial plateau on radiographs could improve the accuracy of conventional surgical techniques.

The Importance of Posterior Tibial Slope in TKR: Pre and Post-Operative Measurements in United States Osteoarthritic Patients

Background: Sagittal plane placement of the tibial component in total knee replacement (TKR) has important implications for maximizing the range of flexion motion, allowing collateral ligaments to function more normally, as well as providing ideal compressive loading on the tibial bone-prosthesis interface. This study attempts to quantify the normal posterior tibial slope (PTS) angle pre-operatively and post-operatively in osteoarthritic patients after using a conventional extramedullary tibial resection guide to assess its effectiveness. Methods: Forty-nine primary cementless total knee replacements in 34 osteoarthritic patients were measured radiographically pre-operatively and one year post-operatively to determine the PTS and its effect on range of motion. Lateral X-rays, using the anterior cortical line of the tibia, were employed for all measurements. Results: Pre-operative PTS measured 11.83˚ (range 5˚ - 18˚), while post-operative PTS of implanted tibial components measured 11.30o (range 4˚ - 18˚). The pre-operative range of motion of 112˚ (range 30˚ to 135˚) was improved to 119˚ (range 90˚ to 135˚) post-operatively after 1 year. Conclusions: Anterior tibial shaft referencing using a conventional extramedullary tibial resection guide provides an easy and convenient method for reproducing the anatomical PTS during TKR. This methodology provided improvement in average range of motion from 112˚ pre-operatively to 119˚ post-operatively at one year.