INTRODUCTION

In patients presenting with significant ligamentous instability/insufficiency and/or significant varus/valgus deformity of the knee, reproduction of knee alignment and soft tissue stability continues to be a difficult task to achieve. These complex primary total knee arthroplasty (TKA) candidates generally require TKA systems incorporating increasing levels of constraint due to the soft-tissue and/or bone deficiencies. In addition, achievement of “normal” gap symmetry through physiologic kinematics is challenging due to the complexity of the overall correction. Advancements in TKA design have not fully addressed the negative consequences of the increased forces between the degree of component constraint, the femoral box, and the tibial post. The purpose of this early feasibility study was to introduce the design characteristics of a primary TKA system that incorporates progressive constraint kinematics using a low profile trapezoidal femoral box, and to assess the short-term clinical and radiographic results of this patient cohort.

INTRODUCTION

Post-operative infections following end-stage joint salvage reconstruction, tumor resection and megaprosthetic reconstruction is a major problem because of increasing infection rates in this patient cohort. The success of treatment and longevity is limited because current prosthetic composites do not decrease infection rates in these patients. Silver coating is an innovative development in the prevention of post-operative infection. Presented here is the current knowledge of the use of silver for this patient population including;

The current knowledge of the use of silver coated prostheses for infection control,

INTRODUCTION

Evolving payment models create new opportunities for assessment of patient care based on total cost over a defined period of time. These models allow for analyses of economic data that was previously unavailable and well beyond our familiar studies which typically include length of stay, surgical complications, and post-operative clinical and radiographic assessments. In the United States, the new Federal program entitled TheBundled Payment for Care Initiative created new opportunities for the assessment of surgical interventions. The purpose of the reported study was to assess the total reimbursement for care as a function of surgical technique in primary total hip arthroplasty (THA).

BACKGROUND

Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation.

Summary

Management of metal on metal hip replacements can be accomplished with a simple algorithm including easily available metal ion levels and hip MRI with metal artifact reducing software. After revision serum metal ion levels can be expected to fall rapidly.

The purpose of this study was to compare the clinical, radiographic, and DEXA results of Epoch® Femoral Component for primary THA with other non-cemented femoral components. The Epoch and Epoch 14+ (Zimmer, Warsaw, IN) Composite Femoral Components were studied in conjunction with the VerSys® Fiber Metal Taper, Fiber Metal Mid coat and Beaded Fullcoat Femoral Components (Zimmer, Warsaw, IN). All patients were randomized into one of five component groups and followed prospectively. All patients across the five groups were matched with respect to demographics and body mass index (BMI) (Table 1). Diagnoses were evenly distributed across all study groups. There was no significant change in BMD at 5-years when compared to the baseline (6 month) DEXA measurements for all component groups except for the Beaded Fullcoat component subset which had significant decreases in BMD in proximal zones 1, 6 and 7, The Fiber Metal Taper showed similar decreases in BMD in zones 1 and 7, and the Epoch Component had a significant decrease in BMD in zone 7 only. Additionally, our DEXA findings complement and support the subjective radiographic interpretations performed for this study cohort. The results from this prospective, randomized controlled clinical trial showed that the Epoch Composite Femoral Component for primary THA can achieve results equal to standard alloy components of varying design. Based on these early results, the Epoch and Epoch 14+ Femoral Components for primary THA are justified for continuance of further prospective study.

Background: Unicompartmental knee arthroplasty was developed as an alternative to the finality of tricompartmental, total knee arthroplasty. Recent short-term and intermediate-term results show favorable results when compared to the first generation results reported in the 1970’s and early 1980’s. The purpose of this study was to report the long-term, single surgeon use of the Allegretto unicondylar knee prosthesis.

Methods: We evaluated 115 medial unicompartmental knee arthroplasties that were implanted by a single surgeon using the Allegretto prosthesis. The average age of the patients at the time of surgery was sixty-eight years. No patients were lost to follow-up. Nineteeen patients were unable to continue long-term office follow-up and were contacted by telephone. Thirty-four patients (thirtyfive knees, 30%) died from unrelated causes. None of the patients that died underwent revision of the index UKA. Thus there were sixty-one patients available for prospective clinical and radiographic evaluation beyond ten-years.

Results: The average time to follow-up for those patients available prospectively was 11.1 years (0.8 years; range, ten years to thirteen years). Clinical evaluations revealed an average pre-operative HSS score of fifty-four points which improved at the most recent post-operative follow-up to an average of ninety-three points. At the most recent average time to follow-up, the post-operative range of motion was assessed at an average of 0.3 degrees of extension through 124.4 degrees of flexion. Radiographically, no component showed evidence of loosening as defined as change in position of the components on serial radiographs. Twenty-one knees demonstrated radiolucencies less than 2 mm of thickness and none were progressive. The Kaplan-Meier survival analysis was calculated and showed a probability of survival of all UKA implants of 97% at thirteen years follow-up (standard error 0.04) with an end-point of revision or radiographic failure.

Conclusions: Provided correct patient selection and technical expertise, the Allegretto UKA system allows for the expected relief of pain, restoration of function and component survival in those patients with medial compartmental knee arthrosis through ten-years.

Introduction and Aims: Currently, multiple femoral component types and sizes exist for primary total hip arthroplasty. However, component sizes for small femoral geometry are generally not available. The purpose of this study is to present the short-term use of a femoral component with sizes that extend into small femoral morphometry applications.

Method: Between November 2001 and December 2003, 20 primary THA cases and three revision THA cases were performed utilising a non-cemented, dual threaded, cone shaped (DTCS) modular femoral component manufactured in off-the-shelf sizes, which include those sizes for small femora. The components are made of CoCr and include a size ‘Z’ (19mm proximal, 9mm distal) and a size ‘Y’ (17mm proximal, 8mm distal). Both components have hydroxyapatite coating for stimulating increased bone on-growth and a modular neck allowing intra-operative adjustments of leg length, version, offset and neck length.

Results: The average patient follow-up was 10 months (range 64 days to 27 months). There were 19 (83%) hips in which the ‘Z’ component was used, and four (17%) hips with the ‘Y’ component. Radiographic evaluation revealed well-fixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Two revision cases (8%) required the additional use of a 6cm modular extension component (MEC) to bridge a proximal femoral deficiency. Two cases (8%) required adjunctive strut allografting at the time of surgery to protect a thin or deficient femoral cortex. There were no reported postoperative complications related to the femoral component. There was no disassociation of the modular neck from the femoral stem and there was no incidence of femoral component fracture.

Conclusion: While expanding component profile offerings into larger sizes is common, developing similar component designs for abnormally small femora is uncommon, beyond the scope of the materials used and only done as a ‘custom’ order. The DTCS modular femoral component used affords a versatile option when presented with cases involving small femoral morphometry. We conclude that the DTCS component in smaller sizes is promising and warranted for continued use.

Introduction and Aims: The incidence and technical complexity of revision total hip arthroplasty (THA) has and will continue to increase dramatically. We report the results of revision THA using a non-cemented, dual threaded, cone shaped, (DTCS) modular femoral component.

Method: Between June of 1999 and July of 2003, 41 revision THAs using a DTCS modular femoral component. Fifty-four percent of the patients were male and 46% were female with an average weight of 84kg (std dev: 30kg, range 57–60 kg), an average height of 170cm (sdt dev: 9cm, range: 155–182 cm) and an average body mass index (BMI) of 26 (std dev: 4, range: 18–31). The average patient age was 71 years (std dev: 12 years, range: 39–85 years).

Results: The average patient follow-up was 16 months (range 6–49 months). The average Harris hip score (HHS) at the most recent time to follow-up was 76. Broken into the HHS component parts, the average pain score was 40 of a possible 44, average motion was nine of a possible nine, and average function was 28 of a possible 47. Radiographic evaluation revealed wellfixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Post-operative complications included recurrent infection in four (10%), subsequently resolved with IV antibiotics; dislocation in three (7%), successfully treated by closed reduction and protective bracing; aseptic loosening in one (2%), with femoral component revision to a larger size; intra-operative periprosthetic fracture in one (2%), treated with ORIF (bone, plate and screws); and a non-union of a pre-revision fracture with subsequent component loosening in one (2%). Regardless of the degree of femoral deficiency, there was no incidence of component disassociation or component fracture.

Conclusion: Revision THA is a demanding undertaking and involves multivariate technical challenges that may include mechanical and material considerations such as prosthetic loosening, prosthetic and periprosthetic fracture. We show that the use of a DTCS modular femoral component affords the surgeon results equal to those reported for revision THA and allows intra-operative versatility independent of bone quality.

We report the results of a cementless modular revision component which has been used in our hospital since 1993. There were 103 patients, in which the aforementioned cementless femoral revision component was used. Patients were evaluated, using both a modiþed HHS and serial radiographs performed preoperatively, at 2 weeks, 3 months and annually postoperatively. The patients were followed for a minimum of 4 years. Pre-operatively, bony defects were classiþed on radiographs according to the classiþcation of Mallory. Three hips were excluded from the evaluation: 1 was lost to follow-up and 2 were deceased. 100 hips with an average follow-up of 75 months were retrospectively reviewed. Indication for revision was aseptic loosening in 96 cases and infection in 4. Average number of previous hip surgeries in this patient group was 2.3. Average pre-operative hip score was 48,8 compared to an average postoperative hip score of 74,4. Postoperative complications included 2 infections and 2 cases of DVT with occurrence of PE in 1 case, 4 postoperative dislocations, 2 cases with radiographic subsidence of the femoral component and 1 case with sciatic nerve lesion. Intraoperative complications included femoral fractures upon dislocation of the hip or impaction of the new stem in 37 cases. At time of latest review there were no clinical or radiographic signs of component loosening. The incidence of postoperative and intraoperative complications are comparable to the literature. Clinical and radiographic results of the cementless, modular titanium revision component are promising and support its continued use.

The measurement of bone mineral density in defined areas around metal implants has improved with the development of dual-energy X-ray absorptiometry. We used this technique to compare the bone mineral density adjacent to metal cementless femoral implants with that of identical regions of bone in normal proximal femora. We studied the anteroposterior views only of 72 femora which contained total hip implants and 34 non-operated femora. We compared the regional bone mineral density of bone adjacent to proximally porous-coated and distally porous-coated implants of one design, to measure the relative differences in the remodelling changes induced by different amounts of porous coating. We also measured differences in bone density with time and with variations in implant size (and therefore stiffness). The greatest decrease in bone mineral density (34.8%) occurred in the most proximal 1 cm of the medial femoral cortex around relatively stiff, extensively porous-coated implants. The next most severe decrease (20% to 25%) was in the next most proximal 6 cm of the medial femoral cortex. Small, progressive decreases in bone mineral density continued for five to seven years after implantation.