Wm Tang

Review article: Knee flexion after total knee arthroplasty

Many factors affect or predict the flexion range achieved after total knee arthroplasty. While the knees that have good preoperative flexion have better final flexion, knees with good preoperative flexion do lose some flexion whereas those with poor preoperative flexion can gain flexion. Although studies of different prosthetic designs have produced conflicting results, recent studies appear to favour posterior cruciate ligament (PCL)—substituting over PCL-retaining prostheses. Several factors related to surgical techniques have been found to be important. These include the tightness of the retained posterior cruciate ligament, the elevation of the joint line, increased patellar thickness, and a trapezoidal flexion gap. Vigorous rehabilitation after surgery appears useful, while continuous passive motion has not been found to be effective. Obesity and previous surgery are poor prognostic factors; certain cultural factors, such as the Japanese style of sitting, offer ‘unintentional’ passive flexion and result in patients with better range. If the flexion after surgery is unsatisfactory, manipulation under anaesthesia within 3 months of the total knee arthroplasty can be beneficial.

Necrotising fasciitis of a limb

Between January 1992 and December 1998, we treated 24 patients with necrotising fasciitis of a limb. There were 15 men and nine women with a mean age of 59.8 years (5 to 86). The infection was usually confused with cellulitis. Exquisite pain and early systemic toxicity were the most consistent clinical features. Diabetes mellitus and hepatic cirrhosis were the most commonly associated medical diseases. One third of the patients died. Those with involvement of the limbs above the knee or elbow on admission had a significantly higher rate of mortality than those with distal lesions (Fishers exact test, p = 0.027). There was no correlation between mortality and advanced age (Students t-test, p = 0.22) or between amputation and survival (Fishers exact test, p = 0.39).

Coronal bowing of the femur and tibia in Chinese: its incidence and effects on total knee arthroplasty planning

Purposes. To study the incidence of femoral or tibial bowing in the coronal plane in a Chinese population, and how it affects the accuracy of bone cuts for total knee replacement when an intramedullary alignment system is used. Methods. Standing radiographs of the entire lower limb of each patient with end-stage primary osteoarthritis of the knee were analysed. All radiographs were digitised and the extent of bowing in the coronal plane measured. A bowing was marked if an angulation was more than 2 degrees. The projected error of cutting was then calculated. Results. Of 93 lower limbs, 58 (62%) of the femurs had marked bowing in the coronal plane; 41 (44%) had a mean lateral bowing of 5.3 (standard deviation [SD], 3.2) degrees; 17 (18%) had a mean medial bowing of 4.4 (SD, 1.9) degrees. Marked tibial bowing in the coronal plane was less common (30 tibias, 32%). If a cutting error of more than 2 degrees was considered unacceptable, significantly more unacceptable cuts would ensue in the groups with marked bowing (p=0.003 for femurs and p<0.001 for tibia, respectively). Conclusion. The incidence of femoral or tibial bowing in the coronal plane was high in a Chinese population with end-stage osteoarthritis of the knee. This phenomenon may increase bone cut errors in total knee replacement if an intramedullary alignment system is used and the extent of bowing is not recognised.

Primary total hip arthroplasty in patients with ankylosing spondylitis

The results of total hip arthroplasty in a group of patients with ankylosing spondylitis are described. Ninety-five arthroplasties were performed in 56 men and 2 women whose average age at operation was 38.9 years (standard deviation [SD], 11.6; range, 19.2-78.8). They were followed for an average of 135.4 months (SD, 81.6; range, 24.4-331.2). We encountered 4 deep infections necessitating the removal of prostheses. Two of 3 dislocations were anterior dislocations. Nineteen arthroplasties were revised at an average of 162.0 months (SD, 49.6; range, 55.1-250.5) after the primary surgery; 9 of them had only the acetabular component revised because of aseptic loosening. Hyperextension of the hips is a common phenomenon that can lead to surgical error and predispose the prosthesis to anterior dislocation.

Computer navigation did not improve alignment in a lower-volume total knee practice

AbstractPostoperative alignment of the implanted prosthesis in computer-navigated TKA has been reported to be superior to that using the conventional technique. There is an assumption that use of computer navigation techniques can make an inexperienced or occasional TKA surgeon perform more like an expert TKA surgeon. To assess improved accuracy in recreation of mechanical alignment in TKA performed using computer navigation, a retrospective review of the experience of one of the authors (WPY) before and after using computer navigation was performed. We reviewed the radiographic results of 104 TKAs (52 computer navigation, 52 conventional technique) and found the accuracy of postoperative radiographic alignment of the implanted prosthesis was not improved by using computer navigation as judged by (1) overall limb alignment (case: varus 1.3°; control: varus 0.3°); (2) femoral component alignment (case: 90.3°; control: 90.3°); and (3) tibial component alignment (case: 89°; control: 90°). Significant factors that affected postoperative overall mechanical alignment in the current navigation series included severity of the preoperative deformity, amount of error in making bone cuts, and experience of the surgeon in using the computer navigation system. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Patellar clunk syndrome after posterior stabilized total knee arthroplasty.

Two hundred thirty-six posterior stabilized total knee arthroplasties (TKAs) were performed consecutively. Twenty-seven patellar clunk syndromes were identified in 25 patients. Insall-Salvati ratio, position of joint line, postoperative patellar height, and anterior-posterior position of tibial tray were measured. It was found that postoperative low-lying patella (P<.001) and anterior placement of tibial tray (P=.011) was associated with patellar clunk syndrome. Thirteen patients had bilateral TKAs of the same prosthesis (5 bilateral AMK knees and 8 bilateral Insall Burstein knees) but unilateral patellar clunk syndrome. The nonclunk sides were used as control for comparison with the clunk sides. The congruency and tilting of the patellar button in the skyline view were documented. It was observed that the congruency of the patellar button was less satisfactory in the clunk side (P=.019).

Review Article: Polyethylene wear and osteolysis in total hip arthroplasty.

Polyethylene wear has been accepted as a major cause of osteolysis in total hip arthroplasty. Submicron particles, which are secondary to abrasive wear, migrate into the effective joint space and stimulate a foreign-body response resulting in bone loss which is mainly mediated by macrophages. Diagnosis depends on serial radiographic evaluation and frequent follow-up. Polyethylene wear and osteolysis can be prevented by reducing the wear such as using a small femoral head, adaptive polyethylene thickness, suitable surgical techniques, non-polyethylene articulation, etc. The presence of cement or circumferential coatings may also retard the distal migration of particles. Medicines such as NSAIDs and bisphosphonate appear to inhibit the progress of osteolysis. As far as treatment, revision surgery is able to reconstruct the joint by replacing partial or total prosthesis and repair the defect by bone grafting according to intraoperative assessment.

Report of 2 Fatal Cases of Adult Necrotizing Fasciitis and Toxic Shock Syndrome Caused by Streptococcus agalactiae

We describe 2 cases of fatal necrotizing fasciitis and toxic shock syndrome caused by Streptococcus agalactiae-a rare entity that has been reported in only 9 patients-in 2 nonpregnant adults.

Silent compartment syndrome complicating total knee arthroplasty: continuous epidural anesthesia masked the pain.

Posterior dislocation is an uncommon complication of total knee arthroplasty (TKA) using a posterior stabilized total knee prosthesis, and it usually results from flexion instability. Acute posterior dislocation of a posterior stabilized prosthesis complicated by compartment syndrome of the leg has not previously been reported in the literature. We report a 62-year-old woman with posterior dislocation of her posterior stabilized TKA when her knee was in extension. It was further complicated by compartment syndrome with severe muscle necrosis. The diagnosis of compartment syndrome was delayed, partly because of continuous epidural anesthesia that completely abolished the pain and partly because of the low index of suspicion, as compartment syndrome is not well recognized as a possible complication of TKA. This case report strongly emphasizes that continuous epidural anesthesia is contraindicated in the case of complicated TKA because important clinical cues to neurovascular complications could be masked.

Efficacy of a single dose of cefazolin as a prophylactic antibiotic in primary arthroplasty.

We analyzed the wound infection rate of 1,367 primary total hip and knee arthroplasties performed between 1991 and 1999. Two hundred and fifteen arthroplasties were performed with 3 doses (3 x 750 mg) of cefuroxime, and 1,152 arthroplasties were performed with a single preoperative dose (1 x 1 g) of cefazolin as antimicrobial prophylaxis. All wound infections that occurred within 2 years of the index surgery were analyzed. The deep wound infection rate of total hip arthroplasty was 1.1% (95% confidence interval [CI], 0%-3.3%) in the cefuroxime group and 1.1% (95% CI, 0%-2.2%) in the cefazolin group (Fishers exact test, P = 1.0). The deep wound infection rate of total knee arthroplasty in the cefuroxime group (1.6%; 95% CI, 0%-3.8%) was not significantly different from the cefazolin group (1.0%; 95% CI, 0.3%-1.7%) (Fishers exact test, P =.63). We concluded that a single dose (1 g) of cefazolin given at anesthetic induction offered similar protection to 3 doses (3 x 750 mg) of cefuroxime in preventing infection in primary total joint arthroplasty.