BACKGROUND: Clinical results at 10–14yrs of the NKI noncemented TKA(AAOS 2005, Plaster) showed no failure of ingrowth and no tibial osteolysis. A similar 10yr study of the NKII series indicated a higher revision rate based solely on tibial osteolysis at the tip of the medial screw, creating a 9% partial revision rate (poly-exchange and grafting of cyst) of NKII at 10yrs. There is no failure of the actual ingrowth bond.

METHODS: Between Dec 1995–01, 1410 pts were implanted with NKIIs (Zimmer). Prospective data was collected at preop, surgery & intervals up to 5–10yrs. Classification of osteolytic cysts is defined: Grade 1=cyst of 1cm; Grade 2=cyst > 1cm without cortial erosion; Grade 3A=cyst < 1cm with cortical erosion; Grade 3B=cyst 1cm with cortical erosion & Grade 4=stress fracture or perosteal reaction indicative of a stress fracture. Specimens from revisions have been evaluated by 2 independent labs. Inserts were replaced using a highly crosslinked poly.

RESULTS: 445 pts were seen for clinical and xray f/u, 65 expired. Osteolysis occurred in 36% most of which were early stages. Revision were required in 9%. Exams of the poly show wear with football shaped extrusions into the screw holes & abrasive scores consistent with micromotion. Microscopic analysis show macrophages with inclusions suggestive of poly debris but there is a paucity of actual poly seen.

DISCUSSION: Osteolytic cysts are occurring in the NKII & not in NKI. It is not known if these are design issues or poly “improvement” issues. One postulation is smaller particles but increasing numbers has led to a decrease in the bone tolerance. Early f/u of highly cross-linked poly shows marked improvement and no cysts.

Generation of the tibial cyst is multifactorial. Implantation techniques can increase poly imminence impingement by the femoral notch thus increasing forces on poly during gait. Lowering the notch on the NKII improves patella contact but can lead to impingement if the surgeon flexes the femur or places too much slope on the tibia. Hydraulic action is also postulated, joint fluid is being forced down the screw channel carrying with it small poly particles. The tight peripheral tolerances of the insert into the baseplate may create such a tight fit that the insert acts like a piston with each step. Lab testing is currently being done to test this hypothesis and evaluate micromotion and wear patterns. We are recommending polyexchanges for stg 3 & 4 pts to the highly crosslinked poly as well as curetting and grafting all cysts. Early results show cyst resolution. Stress fractures may require long stem revision baseplates. Stg 1 & 2 can be followed with serial xrays

BACKGROUND: Historically results of cementless THA with a variety of porous material and design has been sporadic with 5–20% thigh pain. A simple straight tapered stem with anatomic features for proximal load transfer and excellent initial stability was developed in the early 90’s.

METHODS: 196 cementless collared Natural hip stems (Sulzer/ Zimmer) were implanted by a single surgeon using a posterior approach. They were entered into a database prospectively from 1992–95 and followed until 2006. Data was collected preoperatively and at intervals with last follow-up of 10–14 years. Physical exams, SF-36’s, hip assessments, patient satisfaction surveys and radiographs were performed. X-rays were analyzed for radiolucent zones and bone condensation/ remodeling.

RESULTS: 106 have 10 year data with 34 dead and 9 having moved out of state. One femoral component was removed for deep infection. Eight have had liner exchanges for polyethylene wear, 1 acetabulum was revised for recurrent dislocations.

There have been no femoral revisions for loosening and no complete radiolucencies involving the cancellous structured titanium (CSTi). 85% of x-rays show proximal bone condensation with maintenance of a strong calcar. Distal radiodense lines (halo) are present in 20% around the split smooth tip, with 30% showing an asymptomatic midstem cortical buildup.

Average Harris Hip scores at 10 years (including all Charnley classes) was 85. 90% of patients reported either no pain (65%) or slight (requiring no medication). 100% were satisfied with their outcomes. Anterior thigh pain was conspicuously absent occurring in one patient but disappearing the first year.

CONCLUSIONS: The design of the conical tapered stem which includes an anterior buildup proximal, proximal Cancellous Structured Titanium (CSTi), midstem anti-rotational flutes and a split/spread distal tip transmits force to the femur in a graduated load transfer keeping the proximal femur healthy without stress shielding. The split distal stem and decreasing radius provides a long zone of transition for stiffness and prevents thigh pain. The CSTi provides dependable bone ingrowth and seals the canal preventing osteolysis even in cases where there has been acetabular poly wear. X-rays, SF 36’s and clinical results document the success. As a straight stem ream/broach technique, excellent clinical results can be obtained by general community orthopedists using techniques they are comfortable with.