CLS Spotorno expansion acetabular cup is in use since 1984 for uncemented Metal-Polyethylene (PE) total hip arthroplasties (THA). Metal-PE articulations are notoriously known to wear and lead to failure of THA. However, catastrophic breakage of expansion acetabular cup is rare. Our 74-year-old male who was diagnosed with bilateral osteonecrosis of femoral head, underwent bilateral THA using CLS Spotorno metal expansion acetabular cups (Protek, AG, Bern) in 1991. He had irregular follow-up since then. In 2005, he presented with right hip pain and inability to walk without support. Anteroposterior (AP) hip radiographs established the diagnosis of catastrophic failure of right THA secondary to severe liner wear and acetabular osteolysis. Patient chose to postpone the revision surgery and opted for wheel chair ambulation. He presented 4 years later, when the right hip pain became unbearable. Anteroposterior as well as lateral hip radiographs showed worsening of cup breakage with superolateral migration of metal femoral head. Pelvic CT scans confirmed severe acetabular osteolysis in DeLee and Charnley's Zone 1, 2 & 3 with secondary loss of bony support to the expansion cup [Fig. 1]. A revision THA was strongly advised. However, patient sought for a pain-free rather than a fully ambulatory right hip and decided against a second THA. We performed resection arthroplasty of right hip with bone cement loading, respecting patient's decision. Intra-operatively, the metal femoral head was lying in the huge osteolytic defect in the roof of acetabulum. The 3 cranial wings of metal expansion shell were broken with corresponding wear of the cranial pole of polyethylene liner [Fig. 2]. We were able to gratify patient's expectations and patient is able to ambulate with the aid of one crutch at latest follow-up. However, it is clearly evident that a timely and regular follow-up would have identified the initial PE wear and secondary osteolysis. Additionally, it can avoid extensive procedures like a revision THA or resection arthroplasty by allowing simple procedures like modular PE liner and the femoral head exchange. A comprehensive review of literature for catastrophic acetabular component breakage revealed 10 such cases, although with different cup designs. To the best of our knowledge, this is the first case of CLS expansion cup breakage for metal-PE articulation. Majority of these cases have a presence of extensive liner wear and pelvic osteolysis along with a post-operative irregular follow up. This case stresses on importance of regular follow-up even after many years of index THA to identify early PE wear and prevent secondary catastrophic complications

Background. The clinical results of total hip arthroplasty (THA) with a cementless prosthesis have been constantly improving due to progress in the area of stem design and surface finish. However, majority of stems are well-fixed with canal filling or diaphyseal fit, and cortical hypertrophy or metaphyseal bone atrophy has been often observed. Cementless Spotorno stem (CLS stem; Zimmer, Warsaw, USA) is a double-tapered rectangular straight stem. The purpose of this study is to investigate the mean 13 years' results of CLS stem and to evaluate the press-fit stability of CLS stem. Methods. Between 1999 and 2004, we treated 134 patients (142 hips) with CLS stem. Of those patients, 86 females (92 hips) and 13 males (14 hips), in total 99 patients (106 hips) were available at minimum of 11 years after surgery. At the time of follow-up, six females and five males were dead. The follow-up rate was 82% and the mean follow-up period was 13 years (SD; 20, range; 11–16). The mean age at the time of surgery was 65 years (SD; 10, range; 38–86). The mean body mass index was 24 (SD; 1.8, range; 19 to 28). Preoperative diagnoses were osteoarthritis in 92 patients, osteonecrosis in five patients, and rheumatoid arthritis in two patients. Majority of the patients were female because 84 patients of osteoarthritis suffered from hip dysplasia. For cementless acetabular reconstruction, APR cups (Zimmer, Warsaw, USA) were implanted in 10 hips, IOP cups (Zimmer, Warsaw, USA) in 22 hips, and Converge cups (Zimmer, Warsaw, USA) in 74 hips. As the liner of acetabular component, conventional UHMWPE (Sulene: Zimmer, Warsaw, USA) was used in APR cup and highly crosslinked UHMWPE (Durasul: Zimmer, Warsaw, USA) in IOP and Converge cups. The lipped liner was chosen in all cases, and lipped lesion was placed posteriorly. The radiographic stability of the femoral stem was determined by Engh's criteria. The ascertained period of spot welds was noted by Gruen zones on the femoral side. The presence of stress shielding, and subsidence was also evaluated. Results. A stable stem with bony on-growth was identified in all cases. The mean period of expression of spot welds was 11 months in zone 2, 10 months in zone 3, 9 months in zone 5, and 9 months in zone 6. Stress shielding of more than grade 2 was observed in only 8 hips, which was non-progressive at 1 year after surgery. Subsidence of more than 2mm was not observed in any of the hips. The cortical hypertrophy at the tip of stem was not observed. The postoperative dislocation occurred in six hips (6%) and periprosthetic femoral fracture occurred in two hips (2%). Revised surgery was performed in three hips for a recurrent dislocation and two periprosthetic femoral fracture. Conclusions. Excellent stability of CLS stem has been maintained without abnormal bone reaction at proximal femur. CLS stem is considered to achieve not only press-fit stability at trochanteric and subtrochanteric level, but bony fixation by osseointegration within 1 year after THA

Modern prosthetic stem construction strives to achieve the attractive goals of stress shielding prevention and optimal osteointegration. PhysioLogic stem is a new generation composite isoelastic femoral stem consisting of titanium core sheathed in implantable PEEK polymer and coated with titanium layer. This construction combines the benefits of both stress shielding prevention, due to its elasticity under bending load corresponding closely to that of natural bone, and rapid osteointegration, due to the stem's titanium coating. The aim of this study is long-term clinical progress evaluation and retrospective analysis in patients undergoing primary PhysioLogic stem implantation at our institution. From 1998 to 2003, we performed 51 primary total hip arthroplasty (THA) operations with implantation of PhysioLogic Stem at our institution. Indications for THA included osteoarthritis (21), hip dysplasia (14), rheumatoid arthritis (10), and femoral neck nonunion (6). In all patients we used totally uncemented system — PhysioLogic Stem and monoblock cup with different types of bearing surface articulation (40 metal/polyethylene, 3 ceramic/polyethylene, and 8 metal/metal). In all cases head size was 28mm. Two patients died in the early post-op period at day 1 and day 9 from disseminated intravascular coagulation and pulmonary embolism, respectively, and were excluded from subsequent analysis. Analyzed patients included 20 women and 29 men; median age 45, range 21–69. Post-operatively, the patients were evaluated at 3 and 6 months, 1 year, and yearly thereafter. Median follow-up period was 14 years, range 11 to 16 years. Clinical and functional outcomes were evaluated by Harris Hip Score. Bone density in Gruen's and Charnley's zones was measured by dual-energy x-ray absorptiometry. Four patients died at 5–8 years postoperatively from cardiac causes. Two patients underwent revision surgery: one patient underwent “dry revision” due to hip dislocation with exchange for longer head while keeping the original PhysioLogic stem in place; second patient underwent stem removal after chronic periprosthetic infection. Among the 45 patients with surviving PhysioLogic Stem, 33 patients (75%) underwent subsequent contralateral total hip arthroplasty with standard uncemented stems types Spotorno or Zweymuller. These patients were surveyed at postoperative evaluation about subjective comparative performance of PhysioLogic Stem versus standard stem. Twenty seven patients (82%) reported the PhysioLogic stem to be equivalent or superior to the standard stem, with 15 patients (45%) rating the PhysioLogic stem as subjectively more comfortable than the standard stem. The average Harris hip score improved from 40 points preoperatively (range 27 to 48) to 93 points (range 89 to 95) at the time of final follow-up. All stems continue to show adequate bone-ingrown fixation with no radiological signs of aseptic loosening to date. The PhysioLogic stem removed in the aforementioned case of chronic periprosthetic infection also showed clear signs of good osteointegration. Our study showed that the PhysioLogic stem implantation resulted in favorable clinical and functional performance at long-term follow-up, making it an attractive alternative to standard stems

Introduction. Many finite element (FE) studies have been performed in the past to assess the biomechanical performance of TKA and THA components. The boundary conditions have often been simplified to a few peak loads. With the availability of personalized musculoskeletal (MS) models we becomes possible to estimate dynamic muscle and prosthetic forces in a patient specific manner. By combining this knowledge with FE models, truly patient specific failure analyses can be performed. In this study we applied this combined technique to the femoral part of a cementless THR and calculated the cyclic micro-motions of the stem relative to the bone in order to assess the potential for bone ingrowth. Methods. An FE model of a complete femur with a CLS Spotorno stem inserted was generated. An ideal fit between the implant and the bone was modeled proximally, whereas distally an interface gap of 100μm was created to simulate a more realistic interface condition obtained during surgery. Furthermore, a gait analysis was performed on a young subject and fed into the Anybody™ MS modeling system. The anatomical data set (muscle attachment points) used by the Anybody™ system was morphed to the shape of the femoral reconstruction. In this way a set of muscle attachment points was obtained which was consistent with the FE model. The predicted muscle and hip contact forces by the Anybody™ modeling system were dynamic and divided into 37 increments including two stance phases and a swing phase of the right leg. Results. The magnitude and path of interface micromotions was heavily dependent on the location on the implant. In the proximal region, a unidirectional pattern was visible in proximal-distal direction (max. motion was 39μm). Mid stem micromotions were very small (in the order of 4μm), whereas in the distal region, micromotions had a tendency to develop in anterior-posterior and medial-lateral direction (max. motion was 96μm). Hence, in this example, ingrowth is most likely to start in the mid-region. Conclusion. By combining finite element models with musculoskeletal models more realistic, dynamical simulations can be generated to assess the biomechanical behavior of prosthetic components. Both, FE models as well as MS models can be personalized, which offers the possibility to perform truly patient specific predictions. Furthermore, by performing personalized MS and FE calculations, a database is established containing variability of kinematic, force and reconstructive parameters in patients. With this database new implants can be tested in a more robust and reliable manner than before, thereby reducing the chance that innovative ‘defective’ implants are launched on the market