The vast majority of total-joint-replacement components utilized are modular to some degree. Modularity increases the surgeon’s options in both primary and revision THA. Modular prostheses allow the surgeon intra-operative versatility, allowing adjustment of leg length, offset, neck length, and version. This is particularly helpful in CHD, posttraumatic arthritis and in hip revision. Modularity may be applied also to the neck, enlarging the range of choice for difficult cases. Howeverusing of a modular interface increases risk of fretting, wear debris, and dissociation and mismatching of components. A series of 87 revision THA performed between 1997 and 2003 using modular neck was reviewed. The pros-theses are AnCA-Fit with a cementless titanium anatomical stem and Profemur with a tapered revision titanium stem. Both provided with a modular neck inserted by morse taper and a hemispheric press-fitted cup. All the implants have a ceramic-ceramic coupling. Four cases were performed due to recurrent dislocation and 83 for implant loosening. Retrieved necks were studied searching for corrosion. No cases of disassembly or fracture of the neck were observed. Two cases of dislocation were treated with brace. Analysis of retrieved necks confirmed the absence of corrosion. Leg length discrepancy decreased from 57.7% to 22%. One post-operative infection was successfully treated with debridment. Modular neck system allows to correct intraoperatively leg length and offset, choosing between five interchangeable necks available in two lengths: straight, varus-valgus, ante-retroverted. Restoration of hip biomechanics prevents instability. Removal of the neck allows a better surgical exposure when femoral stem is retained. Moreover it allows to maintain ceramic-ceramic coupling. Modular prosthesis has some problems related to risk of corrosion, fretting, fracture or dislocation of components. We observed no cases of disassembly of components or fracture and comparative analysis between retrieved necks and those experimentally studied confirmed absence of corrosion.
MOD-B with antibiotic powder and PMMA Cylinders (A-MB-C) have been placed in saline solution and plasma for 4 weeks, compared with cylinders made with PMMA and antibiotic. The mechanical resistance of A-MB-C to compressive test has been performed subsequently. About biocompatibility, A-MB-C were implanted in sheep’s Ilium. After 3 moths an histologic evaluation has been performed.
The MOD-B + antibiotic + PMMA have released the higher quantity of antibiotic for all the 4 weeks. The A-MB-C resistance has been of 13.6 MPa, the same resistance of cancellous bone in the man’s femur. The histological result with a fluoroscopic microscope has been an osteogenesis in the full section of the cylinders.
Valgus knee is a complex deformity, characterised by varying degrees of flexion, external rotation and valgus deviation. Contracture of external ligamentous structures makes correction and soft tissue balance often difficult and may lead to persistent post-operative instability. Further problems include patellar tracking, bone defects, especially at the external femoral condyle, and the risk of external popliteal sciatic (EPS) nerve palsy after surgery. Krackow distinguished three types of valgus knee: type 1 with integral medial peripheral structures; type 2 with severe medial structure laxity and impossibility to correct passively; and type 3 which is the sequela of over-correction tibial osteotomy. From 1996 to 2003 we performed 64 fusions due to valgus knee in 41 females and 23 males, aged between 55 and 76 years (mean 67.5). Of these, 52 deformities were type 1, nine type 2, and three type 3. For type-1 lesions we always used prostheses with posterior stabilisation (PS), and balanced the capsulo-ligamentous structures. In type-2 lesions we used a vincolo condilare prosthesis with CCK in two cases and a cerniera prosthesis in two cases, whereas in the remaining five cases we used a PS prosthesis. In type-2 deformities we used a PS prosthesis with a modular tibial component with metal augments. Mean follow up was 45 months. Radiographically, valgus deformity fell from 22.4° (10° min – 35° max) to 5.4° (3° min – 9° max). Post-operative results, according to the HSS score, were excellent in 51 cases, fair in 11 cases, and poor in two cases, due to the need to perform revision in two stages in an infected prosthesis 6 months after surgery in one case, and aseptic loosening in another. Valgus knee due to arthritis can be successfully treated by total knee arthroplasty using various techniques, according to the clinical severity. EPS nerve palsy has been cited as a potential problem in total knee arthroplasty. We did not observe this complication in our series, probably because we maintain the knee in continuous slight flexion for the first 18–24 h.
