We retrospectively reviewed all 64 patients with a symptomatic failed primary TKA associated with bone loss who had a revision TKA using cementless long-stemmed components with morselized loose bone graft between 1999 and 2006. The indications for this type of reconstruction were: (1) limiting knee symptoms (pain and stiffness), (2) patient dissatisfaction with knee function, and (3) radiographic changes (progressive loosening with bone deficiency). There were no absolute contraindications specifically related to this type of reconstruction. Two of the 64 patients were lost to followup and six died from unrelated reasons. This left 56 patients available for review. There were 26 men and 30 women with a mean age of 68.3 years (range, 56–89 years) at the time of surgery. The minimum followup was 4 years (median, 7.5, mean, 7.3 years; range, 4–10 years). No patients were recalled specifically for this study; all data were obtained from medical records and radiographs.
Preoperatively, all patients were investigated to ascertain the type of implant failure and to plan the appropriate surgical intervention. All patients had the following investigations: full blood count, inflammatory markers (C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]), weightbearing plain radiographs (AP, lateral, skyline), microbiology analysis (synovial fluid and/or tissue specimens), CT, and technetium (Tc99
) scintigraphy. Radiographic assessment using plain radiographs only is known to underestimate bone loss and further assessment with CT is sometimes necessary [22
]. Causes of implant failure in the 56 reviewed patients included aseptic loosening (37), deep-seated infection (14), patellar maltracking (three), periprosthetic fracture (one), and poor flexion (one). There were 42 single-stage revisions and 14 two-stage revisions (for infection). We classified bone loss using the Anderson Orthopaedic Research Institute (AORI) classification system described by Engh [11
]. There were varying degrees of bone loss from mild to severe (Table ).
Breakdown of the cases in terms of degree of bone loss
We used the Profix® Total Knee System (Smith & Nephew, Memphis, TN, USA) in all our patients. It features a cobalt-chrome primary femoral component, titanium femoral and tibial stems, asymmetric titanium tibial component, a semiconstrained, moderately conforming polyethylene tibial insert, and an inset-designed polyethylene patella with a central fluted post. The components used in our study were all porous-coated. We implanted long smooth fluted stems with a slotted end to prevent toggle, resist axial loading, and provide rotational stability. Polyethylene inserts with a choice of two levels of conformity were used, but none were posterior-stabilized.
We used Whiteside’s technique [37
] in all our patients. All surgery was performed by the senior author (DPP). The procedure was performed with the patient in the supine position with a foot bolster and side support for the surgically treated knee. One dose of intravenous prophylactic antibiotic was given at induction. After preparation of the skin and exclusion draping, a midline incision with a standard medial parapatellar approach [15
] was used to expose the joint. After exposure, removal of the previous components and cement was performed using small osteotomes. This was performed slowly, methodically, and without force, with minimal stripping of soft tissues. We then assessed bone loss by direct observation of osseous defects and according to the AORI classification described by Engh [11
]. A tibial tubercle osteotomy was performed in nine patients to aid eversion of the patella or to facilitate removal of the implants and cement. The tibial shaft was reamed sequentially with increasing size to cortical bone (a length of 150–200 mm in most cases to achieve correct alignment) until a tight fit was achieved in the diaphysis. We used the reamer as the alignment guide and once it was firmly fixed in the medullary canal, the cutting guide was applied over the shaft of the reamer. The tibia was resected at an angle perpendicular to its long axis. Rather than resect more bone to achieve broad seating of the tibial component, the rims were prepared so that at least 25% of the circumference of the rim was flat to achieve partial seating of the tibial base plate. We carefully reamed the femur in a similar manner to the tibia to 150- to 200-mm depth. The reamer was allowed to follow the track of the femur and care was taken to avoid penetration of the anterior cortex. A cutting guide then was applied and a minimal distal cut (5° valgus angle) was made just sufficient to provide one distal surface on which to base the prosthesis. We minimally recut the posterior condyles to allow the femoral implant to engage posterior bone and to provide a posterior surface to aid in rotational stability. Trial implants were inserted, flexion/extension balanced, and restoration of the joint line achieved using distal femoral augmentation where required. Rotational positioning of the femoral component was guided by the epicondylar axis. We inserted the tibial trial component so that the stem fit snugly but not tightly in the diaphyseal medullary canal with the tibial plate abutting against the remaining tibial rim. The trial spacer was inserted with the knee at 90° flexion. The definitive prostheses then were inserted using 1-mm-larger-diameter stems to assist in stable press-fit fixation. We augmented tibial fixation with screws into intact proximal tibial bone in eight early cases. Stem length was selected to be adequate to engage in the isthmus of diaphyseal bone providing toggle control and press-fit fixation on the femoral and tibial sides. We then prepared the graft by mixing freeze-dried morselized allograft (average particle size of 5 mm) with bony reamings from the femur and tibia with approximately 50 mL to 60 mL of the patient’s blood. All bone defects, regardless of location, were lightly finger-packed and were not impacted. The soft tissues then were repaired and the wound closed. We did not treat uncontained defects differently as we believed the broad attachment of the medial quadriceps retinaculum, the capsular ligaments to the tibial flair, and the soft tissues adjacent to the femoral epicondyles provide an effective soft tissue sleeve around the knee, which can be tensioned adequately with the spacer effect of the implants, enabling effective grafting of these defects [39
In cases with a deep-seated infection, we thoroughly and extensively débrided the knee after removing the old components and cement. Multiple specimens (fluid, synovial lining, bone) were sent to the laboratory for microscopy, cultures, and sensitivity analysis. An articulating antibiotic-impregnated knee spacer then was inserted. After repeated washouts with normal saline pulsatile lavage, the soft tissues and skin were closed. The patient was started on a broad-spectrum antibiotic until the microbiology results were available. Progress was monitored closely clinically and biochemically (leukocyte count, ESR, CRP) to ascertain the appropriate time to proceed to the second stage.
Eleven of the 56 patients were provided with a functional knee brace for 6 weeks postoperatively: two to protect intraoperatively repaired collateral ligaments and nine after tibial tuberosity transfer. The remaining 45 patients were allowed free ROM and mobility. In patients who had undergone a tibial tubercle osteotomy, full weightbearing and resisted active extension were delayed until 6 weeks postoperatively. Prophylactic intravenous antibiotics were given at induction and for two postoperative doses. Thromboprophylaxis consisted of elastic stockings and low-molecular-weight heparin.
Patients were followed at 6 weeks, 6 months, 1 year, and then on a yearly basis. Each visit included obtaining a thorough history and performing a full physical knee examination, documenting any abnormal findings, and evaluating active and passive ROM. Functional assessment preoperatively and postoperatively was performed using the Oxford Knee Score (OKS) [23
]. This system is based on a questionnaire containing 12 questions related to activities of daily living, each with five categories of response. Each item is scored from 5 to 1, from least to most difficulty or severity, and combined to produce one score with a range from 60 (least difficulties) to 12 (most difficulties).
Serial standing AP and lateral plain radiographs of the knee were obtained preoperatively and postoperatively, at 6 months, and on an annual basis afterward. Radiographs were assessed separately by two reviewers; an independent radiologist (AGP) and by the first author (SAH) to assess interobserver variability. The analysis included recording the presence of radiolucent defects at the implant-bone interface parallel to the implant margins [14
]. Progression of these lines was recorded when there was an increase in width of 1 mm or greater in any zone. Osteolytic defects were defined as expansive lesions with scalloped margins [13
]. The grafted areas were evaluated carefully at 6 months postoperatively for evidence of change in density, blurring of interfaces in the graft and at the graft-host bone junction, and the occurrence of new trabeculations. Graft incorporation was described as present or not present. Incorporation is characterized by substitution of the old defective bone by living new bone as a result of creeping substitution [35
] (Fig. ). There was no interobserver variability in any of the radiographic observations.
Incorporation and consolidation with new trabeculations are seen across the graft site (arrow).
We used a Kaplan-Meier curve to analyze prosthesis survival with failure as an end point. We defined failure as the need for any additional revision procedure to remove the prosthesis (Fig. A). A second curve was used to analyze the worst-case outcome presuming the two patients who had been lost to followup required revision of their prostheses at the mean followup time (Fig. B). We used SPSS® Version 17 (SPSS Inc, Chicago, IL, USA) for the analyses.
Fig. 2A–B (A) A Kaplan-Meier survival curve with failure of the prosthesis as an end point (need for further revision) shows implant survival of 98% at 10 years (95% CI, 94%–100%). (B) A worst-case survival curve with failure of the prosthesis as (more ...)