High Recurrence Rates of Hyperextension After Total Knee Arthroplasty in Asian Patients With Preoperative Knee Hyperextension: A Prospective Observational Study.

INTRODUCTION: Genu recurvatum is a well-known problem in total knee arthroplasty (TKA) in patients with and without neuromuscular disorders. Hyperextension of the knee joint does not reoccur significantly following adequate correction during TKA is the generally accepted notion. The literature regarding the reoccurrence of genu recurvatum in patients after TKA with preoperative genu recurvatum is scarce. The current study is an intermediate-range follow-up study to assess the pre- and postoperative sagittal plane profiles of Asian patients with genu recurvatum who underwent TKA. Changes in the sagittal profile in the immediate postoperative period were compared with the sagittal plane profile during the follow-up to the time of the final follow-up. MATERIALS AND METHODS: This study was a prospective observational study of 21 patients (35 knees) with preoperative hyperextension of the affected knee who underwent total knee arthroplasty between July 2014 and September 2018, in our centre. The inclusion criteria were patients with primary osteoarthritis of the knee with recurvatum deformity ≥5° as measured preoperatively on a standing lateral radiograph. The exclusion criteria were neuropathic joints, post-traumatic arthritis, inflammatory arthritis, arthritis-associated neuromuscular disorders and revision procedures. The preoperative patients were divided into two groups: those with hyperextension of ≤10° and those with hyperextension of >10°. Radiographic measurements were done using the DICOM software (Kriens, Switzerland). The mean follow-up was 4.7 years (range: 3.6 to 7.6 years), and the minimum follow-up period was 3.6 years. No patients were lost to follow-up. All patients were evaluated clinically pre- and postoperatively using the Knee Society score. The knee range of movement and the coronal and sagittal profiles were recorded using standing radiographs. Statistical evaluation was done using the Chi-square test and the Wilcoxon signed-rank tests (SPSS version 17, Chicago, IL SPSS Inc, 2008). RESULTS: Twenty-one patients (35 knees) with preoperative knee hyperextension underwent total knee arthroplasty with the mean age of patients being 59.38 years and the mean BMI of 32.28. The mean preoperative hyperextension was -10.1° (range: -5° to -26°). Early postoperative sagittal alignment (mean) was +4.5° (3° to 10°), and the mean sagittal alignment at final follow-up was -10.9° (-5° to -15°) (positive values indicate residual knee flexion, and negative values indicate hyperextension). There was no significant difference in the preoperative sagittal profiles of patients with BMI <30 and ≥30 (p=0.43). There was no statistically significant difference (p=0.19) between those with hyperextension of ≤10° and those with hyperextension of >10°. CONCLUSION:  Till now, none of the patients have complained of symptoms related to hyperextension, although the rate of recurrence of hyperextension is high. Long-term follow-up is essential in patients with recurvatum deformity who have undergone TKA since delayed recurrence of hyperextension is possible despite adequate intraoperative correction of the deformity. Accurate preoperative prediction about the magnitude of postoperative deformity is not feasible. It is essential to counsel patients preoperatively that hyperextension may recur even after exercising sufficient care in the operative procedure to minimize its occurrence.

Lateralization of Femoral Entry Point to Improve the Coronal Alignment During Total Knee Arthroplasty in Patients With Bowed Femur.

BACKGROUND: Intramedullary jigs are most often used for distal femoral bone cuts in total knee arthroplasty (TKA). However, the accuracy of bone cuts in the distal femur may be affected by the presence of diaphyseal deformities of the femur. METHODS: Sixty-three patients (88 knees) with lateral bowing of the femur underwent primary TKA using a lateralized femoral entry point for intramedullary femoral guide. The following measurements were obtained on the preoperative and postoperative scanograms-mechanical axis deviation, degree of femoral bowing, femoral entry point from the intercondylar sulcus, distance from the center of the knee to the mechanical axis, and coronal alignment of femoral and tibial components. RESULTS: In 48.8% of cases, the femoral entry point was 3-5 mm lateral to the intercondylar notch, in 44.4% of cases, it was 6-10 mm lateral to the notch, and in 6.8% of cases, it was 10-15 mm lateral to the intercondylar notch. Postoperatively the tibiofemoral angle was 6-10 degrees of valgus in 96% of cases. The postoperative mechanical axis was within 3 mm from the center of the knee in 80 of the 88 knees (90.9%). For every 1° increase in femoral bowing, the entry point was lateralized by an average of 1.04 mm. CONCLUSION: The location of femoral entry point is important in TKA in patients with coronal plane deformity of the femur. In patients with lateral femoral bowing of 5° or more, a lateralized femoral entry point is useful in allowing straighter passage of long intramedullary femoral rod and this resulted in good mechanical axis alignment and femorotibial component alignment in over 90% of patients in our series.

Use of Oversized Highly Porous Cups in Acetabular Revision.

This study assessed the efficacy of highly porous cups in revision total hip arthroplasty for Paprosky types II and III acetabular bone loss. The authors identified 33 acetabular revisions in 29 patients from a prospective database (66% type III, 7 with pelvic dissociation). Initial stability was achieved with interference fit between the anterior inferior iliac spine, pubis, and ischium with cups that were 2 to 4 mm larger than the reamed acetabulum and augmented with multiple screw fixations without allograft or wedges. At mean follow-up of 6 years (range, 2.7-7.7 years) after revision surgery, no dislocation, infection, or reoperation was noted. Mean satisfaction score was 6±3.2. Mean anteversion and abduction angles were 43°±4.6° and 21.5°±4.4°, respectively. Complications included limp in 13% of patients, wound issues in 10%, and heterotopic ossification in 17%. Osteointegration was seen in all cups, without any migration. Mean overall osteointegration, based on the average percentage of the 3 zones in both views, was 55%±21% (range, 25%-95%). The most osteointegration was seen in zone I (superior) and zone VI (posterior), and the least osseointegration was seen in zone II (medial) and zone IV (anterior). This method can provide reproducible results in acetabular revision arthroplasty.