Femoral rotation in ligament balanced knee arthroplasty: a prospective clinical study.

Rotational alignment of the femoral component is an important factor to achieve beneficial results in total knee arthroplasty. Femoral rotation pre versus post surgery was prospectively assessed in 40 patients who underwent ligament balanced knee arthroplasty. Computerized tomography of the knee was performed before and after the surgery to determine the femoral rotation. In 36 out of 40 patients the rotation of the femoral implants differed compared to the preoperative femur (P > 0.001). After surgery the rotational alignment of the femoral component ranged from -3° (internal rotation) to 7° (external rotation). Increased external rotation was found in 33 out of 40 patients ranging from 1° to 7°. These results highlight the importance of individually determined femoral rotation in ligament balanced knee arthroplasty.

Convincing long-term results independent from the postoperative leg alignment following cementless total knee arthroplasty.

BACKGROUND: Cementless primary total knee arthroplasty shows numerous advantages compared with cemented implants (e.g., shorter operation time, preservation of the bone stock). Up to now an increasing number of clinical long-term studies exist. Despite this fact, there is no evidence about the influence of the postoperative leg alignment on the results of cementless knee arthroplasty. There is no work on the clinical outcome of the specific implant, which was used in this study (VANGUARD®, ZimmerBiomet). The purpose of this study was to assess the clinical and radiological long-term results after cementless knee arthroplasty in relation to the postoperative mechanical leg alignment. METHODS: Clinical and radiological results were retrospectively assessed in 83 patients at 10.3 years (ranging from 9.6 to 11.8 years) after implantation. Hip-knee-ankle angle (HKA) was measured, and the patients were separated into a corrected (HKA between three degrees of varus and three degrees of valgus, n = 60) and a varus/valgus (HKA > 3° of varus and valgus, n = 23) group. RESULTS: Up to the time of the clinical follow-up, three out of 83 patients already underwent a revision surgery due to a deep infection (3.6%). Tegner-Lysholm Knee scale was 89.1 in the corrected group and 88.8 in the varus/valgus group (p = .94). The mean Knee Injury and Osteoarthritis Outcome score (KOOS) was 81.2 in the corrected group and 82.4 in the varus/valgus group (p = .63). CONCLUSIONS: Results of this study showed convincing clinical and radiological results after primary cementless knee arthroplasty. Under- or overcorrected postoperative mechanical leg alignments did not influence the long-term clinical results.

Migration characteristics and early clinical results of the NANOS® short-stem hip arthroplasty.

BACKGROUND: Femoral short stems promise essential advantages in total hip arthroplasty. Up to now, only short- and midterm clinical studies exist. Data on early stem migration that could predict later aseptic loosening at an early stage are rare. The purpose of this study was to assess migration patterns and clinical outcome 2 years after hip replacement by a metaphyseal anchored cementless short stem. METHODS: Migration data and clinical results were prospectively assessed in 49 patients. Clinical outcome was measured using the Harris Hip Score (HHS). Migration analyses were performed using the computer-assisted Einzel-Bild-Roentgen-Analyse (EBRA) system. RESULTS: At 2 years after surgery, none of the implants needed revision, and HHS increased from 47.9 up to 98.1. Of 49 patients, 5 (10%) showed increased vertical stem migration (1.5 mm/2a) that might predict late aseptic loosening. Of 49 stems, 44 (90%) showed stable migration patterns indicating a beneficial long-term outcome. CONCLUSIONS: Results of this study confirm the excellent clinical data of previous works. Migration patterns strongly suggest that short-stem arthroplasty is not only an innovative but also a reliable strategy in total hip replacement.

Migration characteristics and early clinical results of a novel-finned press-fit acetabular cup.

BACKGROUND: Ana Nova® is a novel-finned press-fit acetabular cup which showed superior biomechanical characteristics in an experimental set-up. Using Einzel Bild Röntgen Analyse (EBRA) measurements should offer the opportunity to predict implant survival at an early stage. The purpose of this study was to assess migration and clinical outcome 2 years after total hip replacement by a novel-finned press-fit acetabular cup. METHODS: In this study, migration and clinical results of the implant were prospectively assessed in 67 patients. Clinical outcome was assessed using the Harris hip score (HHS). Migration analyses were performed using the computer assisted EBRA system. Data were analyzed for normal distribution using the Kolmogorov-Smirnov test. Group comparisons were performed using the analysis of variance (ANOVA) test. P-values less than 0.05 were considered statistically significant. RESULTS: At 2 years after surgery, none of the implants needed revision and HHS increased from 39.7 up to 92.2. In contrast to the beneficial clinical outcome, 17 of 44 patients showed increased total migration ( 1 mm/2a). CONCLUSIONS: Adverse migration data in this study might predict aseptic loosening and decreased survival of the implant. According to previous studies, it is possible that this effect occurred because of limited accuracy of the EBRA system. In our opinion, migration analyses may not be recommended as a screening tool in a 2 year follow-up.