ABSTRACT
BACKGROUND: Preservation of hip geometry is important for treatment success in endoprosthesis implantation. Digital planning can be used to estimate postoperative hip geometry. This study examined whether digital planning accurately predicts surgical outcomes for two femoral neck resecting short stem implants, Mayo® (Zimmer) and Metha® (Aesculap). METHODS: Preoperative digital planning of the short stem and acetabular cup was performed for 191 patients (197 endoprostheses) with hip osteoarthritis. Digital planning was done with mediCAD II (Hectec) to evaluate types of prosthesis stems and sizes, leg lengthening and offset, and angle of stem inclination within the femur. The predicted values for these parameters were compared to the postoperative measurements. A double coordinate system was developed to measure pelvic and femoral distances separately. Individual scale factors were applied to minimize measurement bias. FINDINGS: Implantation of the planned short stem prostheses resulted in a mean femoro-acetabular leg lengthening of 4.2mm (SD 5.8mm) and a mean femoro-acetabular offset-reduction of 4.2mm (SD 5.9mm) in comparison with preoperative planning. Implantation of both stems resulted in increased valgization compared to planning (Metha®, mean 5.4° (SD 3.7°); Mayo®, mean -3.2° (SD 3.4°)). INTERPRETATION: Differences between preoperative planning and postoperative outcomes were greater for femoro-acetabular than for cup-related leg length and offset. On average, leg length was longer than predicted and there was loss of femoro-acetabular offset. Compared with the planning, valgization of the implanted stems was frequently observed.
Subject(s)
Arthroplasty, Replacement, Hip/methods , Hip Prosthesis , Hip/diagnostic imaging , Osteoarthritis, Hip/surgery , Preoperative Care/methods , Prosthesis Fitting/methods , Female , Femur/diagnostic imaging , Femur Neck/surgery , Humans , Leg/diagnostic imaging , Male , Middle Aged , Postoperative Period , Prosthesis Design , Radiography , Treatment OutcomeABSTRACT
BACKGROUND: More than 300 000 joint replacement operations are performed in Germany every year, and the number is rising. In this article, we consider the question of simultaneous bilateral joint replacement at the hips or knees. Such procedures are indicated in patients suffering from bilateral, symptomatic arthrosis. METHODS: The article is based on a selective review of the relevant literature, and on the authors' own prospective comparative study of simultaneous bilateral hip replacement. RESULTS: The morbidity and mortality of simultaneous bilateral hip arthroplasty are no different than those of a unilateral procedure. Rehabilitation is easier when both joints are replaced at the same time. Simultaneous bilateral knee arthroplasty has comparable morbidity to a unilateral procedure, but a slightly higher mortality (0.30% vs. 0.14%). Allogenic blood transfusion is more likely to be needed in a bilateral procedure, particularly of the knees. Simultaneous bilateral arthroplasty of either the hips or the knees in one surgical procedure is better than two-staged arthroplasty during a single hospital stay. CONCLUSION: Simultaneous bilateral hip arthroplasty is safer for the patient and facilitates rehabilitation, regardless of the patient's age and ASA status (ASA, American Society of Anesthesiologists). With regard to the knees, there are two additional issues, namely the more frequent need for transfusion and somewhat higher mortality of a simultaneous bilateral procedure. Therefore, we recommend simultaneous bilateral knee arthroplasty only for patients in ASA classes 1 and 2. Simultaneous bilateral arthroplasty of either the hip or knee incurs lower costs than two separate operations.
