Rotating hinge knee causes lower bone-implant interface stress compared to constrained condylar knee replacement.

PURPOSE: To compare the stresses at bone-arthroplasty interface of constrained and semi-constrained knee prostheses, using the finite element (FE) method as a predictor of the survivorship of the implants. METHODS: Three-dimensional FE models of the knee implanted with rotating hinge (RHK) and legacy constrained condylar (LCCK) prostheses were generated to study the loads and stresses for two situations: medial- and lateral collateral ligament deficiencies in full extension. RESULTS: On average, the shear stress developed at bone-implant interface dropped from 16.9 to 13.7 MPa (18.9%), and the interface von Mises stress lowered from 37.6 to 30.2 MPa (19.6%) in RHK compared to those in LCCK prostheses. RHK design also resulted in a more uniform stress distribution at the interfaces in both femur and tibia. The average polyethylene liner stress dropped from 9.6 to 2.6 MPa (a 72.7% decrease) in RHK design when compared to that in LCCK design. CONCLUSION: The more uniform interface stress suggests fewer density changes at the periprosthetic regions due to bone remodelling. Moreover, the lower polyethylene stresses are likely to reduce wear and damage. These findings reveal that the RHK design may have more favorable mechanical features compared to LCCK design in full extension boundary conditions, implying a potentially better survivorship. However, the findings should be interpreted cautiously as other configurations were not investigated.

Total knee arthroplasty and patelloplasty in a patient with phocomelia caused by thalidomide.

The treatment of osteoarthritis in patients with phocomelia with total knee arthroplasty is challenging due to the unusual anatomy and severe deformities. The authors present a case of phocomelia caused by thalidomide with end-stage osteoarthritis and grossly medialized patella. The patient was treated with a cemented constrained non-hinged prosthesis and patelloplasty. Six months later, the patient had complete relief of pain and was able to walk without walking assistance. To our knowledge, total knee replacement in a patient with phocomelia caused by thalidomide has not been described in literature.

Condylar constrained knee prosthesis and rotating hinge prosthesis for revision total knee arthroplasty for mechanical failure have not the same indications and same results.

PURPOSE: This study aimed to evaluate whether there are any differences in outcomes and complication rates between condylar constrained knee (CCK) and rotating hinge knee (RHK) prostheses used for the first revision of total knee arthroplasty (rTKA) after mechanical failure. METHODS: Sixty-three consecutive non-septic revisions of posterior stabilized implants using 33 CCK and 30 RHK prostheses were included. Clinical evaluation and revision rate were compared between the two groups at two years minimum follow-up. RESULTS: The CCK group had significantly better clinical outcomes and satisfaction rates compared to patients with RHK (KSS-knee 70.5 versus 60.7 (p < 0.003) and KSS-function 74.9 versus 47.7 (p < 0.004) at 3.7 (2.0-9.4) years mean follow-up. Moreover, the clinical improvement was significantly higher for the CCK group concerning the KSS-Knee (+23.9 vs. +15.2 points, p = 0.03). The postoperative flexion was significantly better in the CCK group compared to the RHK group (115° vs. 103°, p = 0.01). The prosthesis-related complications and the re-revision rate were higher in the RHK group, especially due to patellofemoral complications and mechanical failures. CONCLUSIONS: CCK prostheses provided better clinical and functional outcomes and fewer complications than RHK prostheses when used for the first non-septic rTKA. CCK is a safe and effective implant for selected patients, while RHK should be used with caution as a salvage device for complex knee conditions, with particular attention to the balance of the extensor mechanism.

[Effectiveness of condylar constrained knee prosthesis for destructive hemophilic arthritis].

Objective: To investigate the clinical outcomes of total knee arthroplasty (TKA) by using the condylar constrained knee prosthesis in the treatment of destructive hemophilic arthritis. Methods: Between September 2007 and July 2015, 8 cases (8 knees) of destructive hemophilic arthritis accepted TKA by using condylar constrained knee prosthesis. All patients were male, aged 22 to 56 years, with an average age of 35 years. The disease course of hemophilia A was 3-30 years (mean, 17.3 years). Preoperative range of motion (ROM) was (68.1±32.6)°; the flexion deformity was (14.38±16.13)°. Six patients had valgus of 7-35° (mean, 17.3°), of whom, one had fixed dislocation of patella; and one had varus of 15°. Hospital for Special Surgery (HSS) knee score was 52.5±12.9. Pre-operative X-ray film examination demonstrated narrowing of the knee gap and cystic degeneration of articular cartilage and subchondral bone. Results: All patients achieved primary wound healing, and were followed up 1-9 years (mean, 5 years). Tense blister with common peroneal nerve damage and extension penetrating into distal tibial cortex occurred in 1 case respectively, which were cured corresponding treatment. At last follow-up, the knee ROM and the flexion deformity were significantly improved to (98.1±8.9)° and (0.63±1.77)° ( t=-2.527, P=0.036; t=2.396, P=0.047). At 2 weeks after operation and last follow-up, the HSS scores were significantly increased to 77.3±11.0 and 85.0±9.0 ( P<0.05). X-ray film showed that lower extremity alignment returned to normal in patients with varus and valgus. Conclusion: Good curative effect can be get by using condylar constrained knee prosthesis in TKA for the treatment of destructive hemophilic arthritis.