The posterior tibial slope does not influence the flexion angle in posterior-stabilized mobile-bearing total knee arthroplasty.

BACKGROUND: It remains uncertain whether an increase in the tibial slope leads to better flexion in posterior-stabilized (PS) total knee prostheses. PURPOSE: To compare the intra-operative flexion angle between standard and an additional 10° posterior slope inserts. PATIENTS AND METHODS: Between December 2014 and February 2015, 22 patients (25 knees) who underwent PS mobile-bearing primary total knee arthroplasty (TKA) were included. Flexion angles were measured using either standard or specially-made inserts. Differences in flexion angles between the two situations were analyzed to determine the relationship between changes in flexion angle and pre-operative flexion angle or body mass index (BMI), and between intra- and post-operative flexion angle. RESULTS: The difference between the average flexion angle of standard inserts and specially-made inserts was not statistically significant. Although the correlations between changes in flexion angle due to insert difference and flexion angle, pre-operative flexion angle or BMI were not significant, there was a positive correlation between intra-operative and post-operative flexion at 2 years. CONCLUSION: The results showed an additional posterior tibial slope by 10° did not affect the intra-operative flexion angle. Surgeons performing PS mobile-bearing TKA do not need to excessively slope the tibial bone cutting to improve the post-operative flexion angle. LEVEL OF EVIDENCE: I, Experimental study.

Anterior knee pain after total hip arthroplasty in developmental dysplasia.

Little has been reported on knee pain after total hip arthroplasty (THA). The purpose of this study was to investigate the incidence and mechanism of knee pain after THA. Two hundred fifty-two patients with hip dysplasia were clinically and radiographically assessed for knee pain before and after THA. Incidences of knee pain and patellofemoral alignment were analyzed with reference to postoperative change in leg length, femoral anteversion, and the femoral offset. Anterior knee pain was present in 16 patients (7.3%). Lateral patellar tilt was increased in all patients with knee pain and significantly larger compared to that seen in patients without knee pain. The increased patellar tilt disappeared within 3 months, but symptoms in 4 patients persisted for more than 3 months. The patellar tilt was significantly related to the amount of leg lengthening. This study demonstrates that THA influences the patellofemoral joint via leg lengthening and causes anterior knee pain.

High long-term survival of bulk femoral head autograft for acetabular reconstruction in cementless THA for developmental hip dysplasia.

BACKGROUND: Deficient acetabula associated with acetabular dysplasia cause difficulty achieving adequate coverage of the acetabular component during THA. Autografting with the removed femoral head has been used for several decades to achieve better coverage, but the long-term benefits of this technique remain controversial, with some series reporting high rates of graft resorption and collapse. QUESTIONS/PURPOSES: We evaluated the fate of bulk femoral head autograft for acetabular reconstruction in cementless THA for developmental hip dysplasia. PATIENTS AND METHODS: We retrospectively reviewed 70 patients (83 hips) (68 women, two men) with a mean age of 57 years at index surgery. According to the classification of Crowe et al. for hip dysplasia, 10 hips were classified as Type I, 45 as Type II, 19 as Type III, and nine as Type IV. Minimum followup was 9 years (mean, 11 years; range, 9-14 years). RESULTS: We observed no collapsed grafts. In all patients we observed disappearance of the host-graft interface and appearance of radiodense bands in the grafts bridging host iliac bone and at the lateral edges of the acetabular sockets; remodeling with definite trabecular reorientation was seen in 90%. The 10-year survival rate without acetabular revision for any reason was 94%. The mean Merle d'Aubigné and Postel hip score improved from a mean of 9.1 preoperatively to 17.2 at last followup. CONCLUSIONS: Cementless THA combined with autologous femoral bone graft in patients with developmental dysplasia resulted in a high rate of survival. Structural bone grafting achieved a stable construct until osseointegration occurred. We believe the radiodense bands represent a radiographic sign of successful completion of repair of the deficient acetabulum. Congruous and stable contact of the cancellous portion of the graft to the host bed by impaction and use of improved porous cementless sockets may be associated with successful socket survival. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Repair of experimentally induced large osteochondral defects in rabbit knee with various concentrations of Escherichia coli-derived recombinant human bone morphogenetic protein-2.

Effective therapies for the regeneration of large osteochondral defects are still lacking; however, various approaches have been used. We evaluated the efficacy of Escherichia coli-derived dimeric recombinant human BMP-2 (E-rhBMP-2) for the repair of large osteochondral defects in a rabbit model. Osteochondral defects made in the femoral patellar groove of the knee were treated by transplanting gelatin sponges onto which no or various doses of E-rhBMP-2 were loaded. The outcomes were compared with those of an untreated control group four, 12 and 24 weeks after transplantation. At early time points, the cartilage tissue was repaired in a dose-dependent manner, and bone repair was accelerated in the defects treated with high doses of E-rhBMP-2. At 24 weeks, the repair of cartilage tissue was better with E-rhBMP-2 treatment, even at low doses, than without E-rhBMP-2 treatment. Our findings suggest that the use of E-rhBMP-2 improves and accelerates the repair of osteochondral defects in a rabbit model.

Local delivery of rolipram, a phosphodiesterase-4-specific inhibitor, augments bone morphogenetic protein-induced bone formation.

Recombinant human bone morphogenetic protein (rhBMP) is a promising therapeutic cytokine for the induction of bone formation, but a weak response in humans remains a major hurdle in its therapeutic application. We have previously reported an rhBMP-2-induced increase in the bone mass of mice receiving systemic rolipram, a specific inhibitor of phosphodiesterase-4. To overcome the side effects of systemic administration of rolipram, we examined the effects of its local release. Polyethylene glycol discs were used as a delivery system. The discs were impregnated with rhBMP-2 and rolipram and implanted into the dorsal muscle pouches in mice. Bone formation was assessed by measuring the bone mineral content (BMC) of the formed bone. First, to determine the optimal dose of rolipram, we added 0-5000 nmol rolipram and 5 microg rhBMP-2 to the pellets and found that 500 nmol rolipram was the most effective concentration for inducing bone formation after 4 weeks. Second, to examine the time course of bone formation, we implanted 5 microg rhBMP-2 with 0 or 500 nmol rolipram and killed mice 5, 7, 10, 14, or 21 days after implantation. Bone formation was accelerated in the rolipram group. Finally, to determine the rolipram-induced increase in the effect of BMP, BMC obtained after treatment with 5 microg rhBMP-2 and 500 nmol rolipram was compared with that obtained after treatment with 5-9 microg rhBMP-2 without rolipram, 4 weeks after implantation. The results indicated that 500 nmol rolipram enhanced the effect of rhBMP-2 by almost 1.5-fold. In summary, locally released rolipram enhanced the capacity of rhBMP-2 to induce bone formation, an effect previously reported with systemic administration. These findings may decrease the cost and increase the efficacy of rhBMP-2 treatment.

Low levels of steroid-metabolizing hepatic enzyme (cytochrome P450 3A) activity may elevate responsiveness to steroids and may increase risk of steroid-induced osteonecrosis even with low glucocorticoid dose.

BACKGROUND: The main purpose of this study was to examine the relationships among osteonecrosis, steroid-metabolizing hepatic enzyme (cytochrome P450 3A; CYP3A) activity, and steroid dose to determine whether it is possible to prevent osteonecrosis in animals with low hepatic CYP3A activity by reducing exogenous steroid doses. METHODS: Japanese white rabbits (n = 103) were divided into three groups: a group with CYP3A activity induction (by intramuscular phenobarbital injection, n = 31), a group with CYP3A activity inhibition (by oral itraconazole administration, n = 30), and a control group (n = 42). Three weeks later, all rabbits received a methylprednisolone injection. Each group was divided into two subgroups by dosage of methylprednisolone (5 or 10 mg/kg body weight). Three weeks after methylprednisolone injections, the animals were killed and histological examination was performed to determine the incidences of osteonecrosis in the six subgroups. RESULTS: Incidence in the inhibition subgroup with 5 mg/kg steroid was higher than that in the induction subgroup receiving 10 mg/kg steroid. Thus, suppression of CYP3A activity significantly increased vulnerability to steroid-induced osteonecrosis, while increased CYP3A activity reduced this vulnerability. CONCLUSIONS: These findings suggest that low CYP3A activity may be vulnerable to the effect of steroids and increase risk of osteonecrosis, even with a low dose of steroid.

Total hip arthroplasty of dysplastic hip after previous Chiari pelvic osteotomy.

INTRODUCTION: Many reports have suggested that Chiari pelvic osteotomy would improve the results of acetabular component placement and fixation in subsequent total hip arthroplasty. However, little is known concerning the biomechanical, radiological, and clinical effects of Chiari pelvic osteotomy on subsequent total hip arthroplasty. MATERIALS AND METHODS: Ten total hip arthroplasties for developmental dysplasia of the hip after previous Chiari pelvic osteotomy (Chiari group) were compared with 20 total hip arthroplasties for developmental dysplasia of the hip without previous surgery (control group). Preoperative patient demographic data and operative technique were well matched between the groups. The mean duration of follow-up was 3.0 years. Biomechanical, radiological, and clinical evaluations were performed. RESULTS: No acetabular or femoral components exhibited loosening. All patients had good or excellent clinical score according to the Merle d'Aubigne-Postel rating system at the most recent follow-up. Abductor force and joint force were smaller in the Chiari group, although long operative time, more blood loss, and verticalization of joint force were noted in this group. CONCLUSION: This limited study suggested that Chiari pelvic osteotomy changed the biomechanical features of the hip joint, and that this alteration might have compromised subsequent total hip arthroplasty.

Acetabular component orientation in 834 total hip arthroplasties using a manual technique.

UNLABELLED: Acetabular component orientation during total hip arthroplasty affects dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. New total hip arthroplasty navigation systems have been introduced to avoid the errors reported after acetabular component orientation using a manual technique. We investigated acetabular component orientation in 834 consecutive primary total hip arthroplasties performed by one surgeon using a manual technique. We examined the relationship between dislocation and a defined safe range. Vertical tilt and planar anteversion were 44.4 +/- 6.5 and 17.9 +/- 6.3 (mean +/- standard deviation), respectively. The error of vertical tilt and planar anteversion were 5.2 +/- 3.9 and 5.3 +/- 4 (mean +/- standard deviation), respectively. Two hundred thirty-three of 834 hips (27.8 %) were outside the safe range. Logistic regression analysis showed that patients with Group IV class according to the classification system of Crowe et al and right hips had a greater risk of being outside the safe range. Navigation systems should be considered, especially in patients with highly dislocated hips. We found no relationship between risk of dislocation and the safe range. Factors other than acetabular component orientation also might affect dislocation. LEVEL OF EVIDENCE: Prognostic Study, Level IV (case series).