The success of cementless fixation in performance of total hip arthroplasty (THA) can depend on the surgical technique, implant design, and surface structure¹⁾. Surgical technique and implant design are critical for ensuring initial stability while the surface structure of the prosthesis is essential for biological fixation with secondary osseointegration²⁾. Thus, several prosthetic surface structures have been developed for achievement of biological fixation^3-6). Mesostructured surfaces with a pore size of 100 to 2,000 μm and a porosity of 40% or higher can replicate a surface structure similar to that of cancellous bone morphology and enhance osseointegration^7,8). The Lübeck (GHE; ESKA/AQ Implants) spongy metal hip prosthesis (Fig. 1), developed in 1983, is composed of a cobalt-chromium alloy with a fully porous structure designed to closely resemble that of cancellous bone. The surface structure of this implant has a pore size ranging from 800 to 1,500 μm and a depth of 3,000 μm, with an overall porosity of 60%, which may be helpful in promoting osteogenesis^3,9). Several studies have reported ‘good’ to ‘excellent’ mid- to long-term results for use of the Lübeck^10-14). Gerdesmeyer et al.⁹⁾ reported ‘good’ long-term results with a 19-year survival rate of 93.7% for stems and 82.3% for cups after THA using the Lübeck in 79 patients under 65 years of age. This case report describes a patient who underwent THA using the Lübeck more than 25 years ago who underwent revision surgery for management of two periprosthetic femoral fractures and a stem fracture.

Figure 1. The metal-cancellous cementless Lübeck prosthesis (GHE; ESKA/AQ Implants).

An 85-year-old female patient underwent THA of the left hip using a Lübeck hip prosthesis at age 60 at another hospital. There were no postoperative complications, and the patient was capable of satisfactorily performing activities of daily living (ADL). However, approximately six years ago, the patient suffered a stem fracture and a periprosthetic femoral fracture. Because the patient’s memory and account of the incident were vague, details regarding the condition of the fracture and treatment at the time could not be obtained. Conservative treatment was applied, and bony union with marked shortening and displacement of the left femur was observed, and a fracture site located on the stem was identified (Fig. 2). Following achievement of bone fusion, the patient showed recovery to the point where she was able to walk while using a walker; however, six years after the initial fracture, she fell, which resulted in difficulty walking. The patient was referred to our hospital to undergo revision surgery. At the time of the initial visit, a femoral subtrochanteric fracture and a fracture of the Lübeck stem was observed on a plain radiograph of the left hip. A radiolucent line was observed in the proximal portion of the stem, and the distal portion of the stem was well fixed (Fig. 3, 4). Surgery was performed in the lateral decubitus position using a direct lateral approach. Following joint transection of the gluteus medius and gluteus minimus muscles from the greater trochanter, resection of the proximal femur up to the tip of the stem was performed, with selection of a proximal femoral replacement stem (GMRS Proximal Femoral Component; Stryker Orthopedics). The stem anteversion was set at 20° using a mechanical alignment guide¹⁵⁾. Suturing of the detached abductor and vastus lateralis muscles was performed, resulting in overlapping in the hole of the stem. To reduce the risk of dislocation related to cup preservation, performance of cup revision using a dual mobility cementless cup was planned (Trident II Tritanium; Stryker Orthopedics) (MDM X3 Mobile Bearing Hip System; Stryker Orthopedics). No obvious loosening of the cup was observed during surgery, and removal was relatively easy. Cup placement was performed using computed tomography (CT)-based navigation (CT-based Hip Navigation Version 1.1; Stryker Navigation) with an inclination angle of 40° and an anteversion angle of 20°. Replacement of the high hip center was authorized and allogeneic bone grafting was performed on the acetabular side of the bone defect (Fig. 5). Surgery time was 122 minutes with blood loss of 496 mL. At the site of femoral excision where the distal portion of the stem was fractured, gross observation showed that the stem was firmly fixed to the cortex in the longitudinal section, and removal of the stem was difficult, even on the table (Fig. 6). No complications such as postoperative infection, deep thrombosis, or dislocation during the perioperative period were observed. One year after surgery, the patient was able to walk while using a walker and has shown almost complete recovery from her pre-fracture ADL. Overall strength of postoperative abductor muscle remained at manual muscle test 3. The modified Harris hip score during the last follow-up period was 55.0 points.

Figure 2. A plain radiograph before the second fracture. (A) Frontal view. (B) Lateral view. Left femur showed bone union with marked shortening and displacement, and a fractured Lübeck stem.

Figure 3. A plain radiograph taken during the initial visit after the second fracture. A femoral subtrochanteric fracture of the left hip and a fracture in the Lübeck stem. Partial perforation was observed in the medial wall of the acetabulum. (A) Anteroposterior view. (B) Lateral view.

Figure 4. Computed tomography at the initial visit after the second fracture. (A) A radiolucent line (white arrows) was observed in the proximal portion of the stem. (B) The stem was well-fixed distal to the fracture.

Figure 5. Gross findings of the excised femur distal to the fracture site including the distal stem. Gross observation showed that the Lübeck stem was firmly fixed to the cortex.

Figure 6. A plain radiograph after revision total hip arthroplasty. (A) Anteroposterior view. (B) Lateral view.

Previous studies have reported ‘good’ to ‘excellent’ mid- to long-term results using the Lübeck^9-14). In a 2- to 6-year follow-up study of 59 patients (66 hips) under the age of 65 reported by Sugano et al.¹²⁾, the clinical outcome for all hips was rated as either ‘excellent’ or ‘good’, and none of the patients underwent revision surgery. According to Götze et al.¹⁴⁾ of 137 THAs performed using a Lübeck, the survival rates at 14.9 years were 90% for the cup and 86% for the stem. Gerdesmeyer et al.⁹⁾ reported a 19-year survival rate of 93.7% for stems and 82.3% for cups in 79 patients under the age of 65, which has also been reported in subsequent long-term follow-up studies of the same patient group. In a mean 30-year follow-up study of 23 hips, the overall rate of stem survival was 82.6% and the rate of cup survival was 52.2%¹⁶⁾. However, by contrast, stem fractures have been reported as a complication after THA using the Lübeck^13,14,17). Matsui et al.¹³⁾ reported on 51 cases of an implanted Lübeck for treatment of dysplastic osteoarthritis and a follow-up period of five to nine years after surgery. Revision was required in one case due to a stem fracture. Götze et al.¹⁴⁾ reported stem fractures without major trauma in four of 137 cases (2.9%). Kishida et al.¹⁷⁾ critiqued the high rate of stem fractures. Additional surgeries were required for five out of 201 stems due to mid-stem fractures. The authors, who reported significant correlation of champagne-fluted femoral canals and low canal fillings 1 cm below the lesser trochanter with incidence of stem fractures, concluded that the fractures might be attributed to a combination of lack of proximal support, a champagne-fluted canal, a fully porous stem composed of a cast cobalt-chrome alloy, and the narrow dimension of the stem core. In addition, some studies have reported that performance of revision THA was difficult due to the rigid fixation of the distal portion of the stem. Kishida et al.¹⁷⁾ reported on the difficulty of removing the distal portion of the stem, which required a femoral fenestration. In addition, follow-up was conservative in two out of five cases, despite the fact that the stems had been fractured. Götze et al.¹⁴⁾ also reported on conservative treatment of two out of four cases of stem fracture because there were no complaints of pain. In the current case, the radiological findings before revision THA were similar to those reported by Kishida et al.¹⁷⁾, with observance of a radiolucent line located in the proximal femur, a narrow medullary canal located in the distal region, and a well-fixed distal stem. Stress shielding may have shown proximal progression due to performance of distal fixation using a narrow Lübeck stem inserted into a champagne-fluted femoral canal. When considering the current case according to previously reported cases, first, a fracture of the stem occurred at the boundary between inadequate fixation at the proximal portion and rigid fixation at the distal portion. The patient was monitored conservatively at that time. However, gradual loosening of the proximal stem, resulting in a fracture of the femur at the level of the stem fracture is possible. Although the indications for additional conservative treatment can only be estimated, bone fusion was achieved with conservative treatment. However, a second femoral fracture occurred as a result of the fall. A modified extended trochanteric osteotomy has been used in cases of revision THA using a well-fixed stem that will not loosen for fenestration of the femur and removal of the stem¹⁸⁾. In addition, creation of a circle with metal mesh, followed by performance of revision THA with impaction bone grafting (IBG) using an allogeneic bone graft and a cemented stem is the first choice for reconstruction of extensive bone defects in the proximal femur. In this case of stem revision, following removal of the loosened proximal portion of the stem, the distal portion of the implant—which was firmly fixed to the femur—was removed by fenestration as described by Kishida et al.¹⁷⁾. Femoral reconstruction is regarded as a combination of osteosynthesis with plate fixation and IBG with a cemented stem¹⁹⁾. The proximal portion of the stem fracture was loose, and relatively easy removal of the implant was anticipated. By contrast, although difficult, the distal portion could be removed by fenestration of the femur. In addition, reconstruction of the proximal femur following stem removal was complicated by significant shortening and malunion of the fracture site, which was subsequently re-fractured, further impeding correction of the deformity, IBG procedures, and stem insertion alignment. The previously mentioned procedures are complicated and were considered too invasive for application to an 85-year-old patient with dementia and low ADL. Therefore, the proximal femur and distal stem tip were removed, and revision THA was performed using a proximal femoral replacement stem (GMRS), with an emphasis on avoiding deep infection and deterioration of the patient’s general condition due to blood loss attributed to prolonged surgery. We also considered that rehabilitation after extensive IBG or osteosynthesis surgery, such as partial weight-bearing, may be difficult for an elderly patient with dementia. On the acetabular side, assessment of cup movement and loosening was difficult due to the lack of X-ray images after the initial surgery, and we had no information on the liner and head implants. The cup was replaced with a dual mobility cup to promote preservation and to reduce the risk of dislocation. There were no perioperative complications and based on the operative time (122 minutes) and blood loss (496 mL), revision surgery could be performed on an elderly patient with minimal invasiveness. One year after surgery, the patient, living in a senior living facility and able to walk without pain using a walker, expressed satisfaction with the surgical results. The Lübeck stem can provide excellent initial fixation and satisfactory long-term results can be expected due to osteogenesis in the porous portion of the stem. However, stress shielding at the proximal portion in femoral canal geometries such as the champagne-fluted femoral canal, may be caused by rigid fixation and osteogenesis at the distal portion of the stem. In addition, understanding that treatment will be difficult in cases of revision or stem fracture is important. Therefore, to avoid complications such as proximal loosening and stem fracture, adequate preoperative planning is required and use of a femur should prioritize proximal fixation. Even without a stem fracture, if revision is required, removal of a distally well-fixed stem and femoral reconstruction should be considered on a case-by-case basis.

Although Lübeck stem fractures have been reported, no studies examining detailed surgical procedures or postoperative outcomes for revision THA after a stem fracture have been reported. Therefore, this case is considered valuable.

In conclusion, this case report describes an elderly patient who underwent THA using a Lübeck prosthesis who suffered a stem fracture and two periprosthetic femoral stem fractures 20 years after the initial surgery. Revision THA with proximal femoral resection was considered a useful procedure for treatment of a Lübeck stem fracture in an elderly patient with a well-fixed distal stem.

No funding to declare.

No potential conflict of interest relevant to this article was reported.