Richard S. Laskin

Infection in total knee replacement: a retrospective review of 6489 total knee replacements.

Six thousand four hundred eighty-nine knee replacements were done in 6120 patients at the authors’ institution between 1993 and 1999. Operations were done in a theater with vertical laminar flow and with the surgical team using body exhaust suits. Of these knee replacements, 116 knees became infected and 113 were available for followup. One hundred of the infections occurred in patients undergoing primary knee replacement, whereas the remaining infections occurred in patients undergoing revision knee replacement. Ninety-seven of these knees (86%) had deep periprosthetic infections and the remaining 16 knees had superficial wound infections. One third of the deep infections occurred within the first 3 months after surgery and the remaining ⅔ occurred after 3 months. The overall early deep infection rate for patients undergoing a primary knee replacement was 0.39%, whereas the rate for patients undergoing a revision knee replacement was 0.97%. A cohort of noninfected knee replacements from patients matched for gender, age, and month of surgery was used as a control group. Those comorbidities that were statistically significant in increasing the risk of infection were prior open surgical procedures, immunosuppressive therapy, poor nutrition, hypokalemia, diabetes mellitus, obesity, and a history of smoking. Patients undergoing revision procedures had a statistically higher risk of infection than did patients undergoing primary surgeries. If the surgery took longer than 2.5 hours, the risk of infection was increased significantly. There was no change in the infection rate when the perioperative antibiotic prophylaxis was decreased from 48 to 24 hours after surgery. The predominant infectious organisms were gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus Group B). Twenty percent of the knees that were infected clinically had no organisms that could be identified. In each case, the patient had been treated empirically at another institution with antibiotics before a culture of the joint was obtained.

Minimally invasive total knee replacement through a mini-midvastus incision : an outcome study

Total knee replacement traditionally has been done through an anterior incision approximately 18 cm long, using a capsular incision that separates the interval between the rectus femoris and vastus medialis musculature. Although giving excellent exposure, this incision also disrupts the suprapatellar pouch and may lead to adhesions and difficulty with rapidly regaining flexion. It is hypothesized that, by using a more minimally invasive incision, there will be a more rapid return of flexion and the patient will require fewer narcotic medications postoperatively. This retrospective review compared 32 total knee replacements done through a minimally invasive mini-midvastus approach with 26 total knee replacements done through the standard medial parapatellar approach. Preoperative Knee Society scores and postoperative functional outcomes were compared. Postoperative flexion was measured daily during hospitalization and at a 6-week and 3-month followup. Pain was assessed by a visual analog scale and the amount of pain medication used during hospitalization. Implant position was measured. The MIS group had an average skin incision length of 12.8 cm. Passive flexion on a daily basis was significantly higher in the MIS group compared with the standard group. At 6 weeks postoperatively, the change in Knee Score was statistically higher in the MIS group and the average visual analog pain score and the total amount of pain medication was lower. The radiographic alignment and position of all the components was normal in all patients in both groups. The limited disruption of the extensor mechanism results in more rapid restoration of the quadriceps muscle control.

Unicompartmental Knee Replacement: Some Unanswered Questions

Within the past 5 years, there has been a resurgence of interest in doing unicompartmental knee replacement, which was encouraged by reports of easier recuperation, decreased hospital stays, and good functional results. Before doing a unicompartmental replacement, the surgeon should answer four important questions: Is the disease truly unicompartmental? Can this be determined on a clinical examination and standard radiographs, or are more sophisticated studies such as a bone scan or an arthroscopy required? Second, if the patient does have unicompartmental disease are there any specific contraindications to the surgery? The absence of an intact anterior cruciate ligament, and presence of an inflammatory arthroplasty have been said to be contraindications. Is crystalline arthropathy a contraindication? What are the limits of fixed deformity in varus or flexion that can be corrected by a unicompartmental replacement? Overcorrection of angular deformities has in the past led to increased wear of the opposite compartment. Therefore, how much should the knee be corrected? What surgical technique should the surgeon consider? Should the tibial components be inset into the bone or onset. Although it has been alleged that instrumentation is not necessary, obtaining proper alignment often cannot be obtained without the use of instruments. Finally, should the implants be inserted with or without acrylic cement, and what is the minimal polyethylene thickness that is permissible?

Flexion space configuration in total knee arthroplasty

Equal resection of the posterior femoral condyles combined with a 90 degree tibial resection results in a trapezoidal flexion space. Two groups of patients were studied; in one group, the flexion space was allowed to remain trapezoidal, whereas in the other group, the anteroposterior femoral resections were externally rotated to allow rectangularization of the flexion space. In the second group, the range of flexion was increased and the incidence of medial tibial pain and zone I radiolucencies decreased. Other than for knees in a hypervalgus position before surgery, the mean amount of rotation required was 3 degrees +/- 0.2 degrees.

Minimally invasive total knee arthroplasty: the results justify its use.

A mini-midvastus capsular incision was used in a feasibility study of 100 patients having primary total knee arthroplasty. Patients with marked limitation of motion were excluded from the study. Patients were followed up for a minimum of 2 years after surgery. The exposure yielded excellent results clinically and radiographically with restoration of stability and motion. The length of the skin incision varied from 8 to 15 cm with a mean of 10.5 cm. Using the limited exposure did not result in implant malpositioning. The surgical approach was not applicable in patients with a BMI > 40 or in those patients with a severe fixed valgus deformity. Level of Evidence: Therapeutic study, Level IV-1 (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Randomized trial of epidural versus general anesthesia: outcomes after primary total knee replacement.

To compare the effects of epidural anesthesia and general anesthesia on early postoperative outcomes after unilateral primary total knee replacement, 262 patients were randomly assigned to receive either epidural or general anesthesia. All patients received a common rehabilitation protocol including a standardized assessment of progress. One hundred eighty-eight patients received a common thromboembolic prophylaxis protocol with postoperative aspirin, and had a standardized surveillance protocol to detect thromboembolic complications. Deep vein thrombosis was determined by venography on the operative limb, and pulmonary embolism was determined by comparison of preoperative and postoperative lung perfusion scans. The epidural anesthesia group reached all rehabilitative milestones earlier postoperatively than did the general anesthesia group, with a statistically significant earlier attainment of stair climbing. The incidence of deep vein thrombosis was 40% with epidural anesthesia, and 48% with general anesthesia. There were no clots proximal to the popliteal veins. The incidence of pulmonary embolism on lung scan was 12% with epidural anesthesia and 9% with general anesthesia. Epidural anesthesia is associated with more rapid achievement of postoperative in hospital rehabilitation goals after total knee replacement. A minor reduction in postoperative deep vein thrombosis rate was observed with epidural anesthesia, but this did not reach statistical significance. No difference in early postoperative pulmonary embolism was observed between the 2 types of anesthesia.

Total knee replacement with posterior cruciate ligament retention in patients with a fixed varus deformity

A group of patients with a preoperative varus contracture of at least 15 ° underwent total knee replacement with retention of the posterior cruciate ligament. Their outcomes at 10 years were compared with a group of patients with similar contractures in whom a posterior stabilized implant was used, and to a group of patients in whom there was no contracture. In the contracture group where the posterior cruciate ligament was retained, there was an increased incidence of pain, an increased incidence of bone cement radiolucencies, and a decrease in the eventual flexion arc. There was likewise an increased revision rate and a decreased survivorship. In patients with such contractures, the posterior cruciate ligament is a part of the deformity; the deformity cannot be corrected by medial release procedures alone. All these results suggest that for the patient with a fixed varus contracture a posterior cruciate release should be performed and a posterior stabilized type of implant used.

An oxidized Zr ceramic surfaced femoral component for total knee arthroplasty

A ceramic surfaced oxidized Zr femoral component was used in total knee replacemdent. Prior mechanical testing had shown a decrease in adhesive and abrasive wear using this material as compared with CoCrMo suggesting its use in younger patients in whom long-term PE wear is a consideration. The alloy had no demonstrable Ni impurities and was applicable to patients with Ni or Co allergies. In a randomized prospective study comparing femoral components of the same design but fabricated either of cast CoCrMo or oxidized Zr, there was a more rapid return of flexion and regaining functional milestones in the oxidized Zr group. No adverse effects had been observed at the 2-year evaluation.

Joint line position restoration during revision total knee replacement.

Forty-five consecutive knee replacement revision operations done in 44 patients with a revision indication of instability were reviewed. In more than ½ of these patients, the prosthetic joint line was malpositioned proximally. At surgery, the joint line was restored through the use of distal femoral augments and balancing of the flexion and extension spaces. The fibular styloid and medial epicondylar reference points were used to determine proper position of the joint line. Scarring or laxity of the patellar tendon rendered the use of the Insall-Salvati ratio for determining joint line position inapplicable in these patients having revision knee replacement.

The Genesis total knee prosthesis: a 10-year followup study.

This current author reports on the results of 100 consecutive patients with osteoarthritis who underwent a primary cemented total knee replacement using the Genesis prosthesis and who have been followed up for at least 10 years after surgery. In patients in whom the posterior cruciate ligament was sacrificed (combined flexion and angular deformities > 15° to 20°) a posterior-stabilized cam module was affixed to the femoral component and a posterior-stabilized polyethylene was used. More than 95% of patients in both groups had excellent pain relief. The mean flexion was 114° in the group of patients in whom the posterior cruciate ligament was sacrificed and 117° in the group of patients in whom the posterior cruciate ligament was retained. Partial bone cement tibial radiolucencies were seen in 12% of the patients in whom the posterior cruciate ligament was retained and 2% of the patients in whom the posterior cruciate ligament was sacrificed. At 10 years, 76% of the group in whom the posterior cruciate ligament was retained had excellent results and 20% had good results. In the group in whom the posterior cruciate ligament was sacrificed 75% had excellent results and 23% had good results. The survivorship was 96% in the group of patients in whom the posterior cruciate ligament was retained and 97% in the group of patients in whom the posterior cruciate ligament was sacrificed.