Total knee replacement in the post patellectomy patient

Selected decreased 29% in actual dollars and 77% in inflation adjusted dollars during this period. In sharp contrast the cost of knee in@ants increased from 13% of the hospital cost of TIW in 1983 to 25% of the hospital cost of TKA in 1991. The average prosthesis cost increased 118% in actual dollars frum $1,359 in 1983 to $2,960 in 1991. In inflation adjusted dollars the implant cost increased 59%. Wing this period the co-r price index increased 37%. Control of hospital cost for TIQ in the 1980s was achieved through utilization review and control. Unit costs were not controlled. Specifically knee implant costs were not controlled. Cost containmznt for total joint arthroplasty during the 1990s will require control of implant costs.

PAPER

#24

HYBRID FIXATION TlBIAL PROSTHESIS: Early Clinical Radiographic Results and Retrieval Analysis James A. Shaw, M.D., M.S.Hershey Medical Center, 500 University Hershey, Pennsylvania

and Dr.,

A prosthetic tibial component has been developed with design features for hybrid fixation and modular assembly. The surface beneath the tibial tray has been specifically adapted for acrylic cement fixation. A central stem and two peripheral fixation lugs incorporate porous surfaces proximally. This combination affords the component the immediate stability of cement fixation and the potential long-term stability of biological tixat’gn. The two fixation modalities act in concert. The cement allows sufficient stability for ingrowth to occur. The ingrowth surfaces (coupled with the central stem) shield the cement interface from the

tensile

lift-off

forces

which

result

from

eccentric

loading,

while

avoiding the fretting and osteolysis associated with screw fixation. A disassembly capability allows the tibial tray to be removed from the stemmed anchorage assembly. This allows direct access to the porous surfaces for component removal without destructive bone loss. Mechanical testing has identified no structural failures with a 420 kg. (six times body weight) load applied eccentrically to an unsupported tray for 10 million cycles and no evidence of fretting wear. Pull-off testing verified immediate fixation capabilities superior to cemented porous coated trays of identical size and shape. Strain gauge testing has identified a nearly physiological loading pattern in the proximal tibia with this component. Over 300 components have been inserted at Hershey over the last 48 months. None have loosened. A clinical and radiographic review of 50 consequentive primary total knee arthroplastiea with a mean follow-up of 35 months revealed stable interfaces with no progressive radiolucenciea and minimal remodeling changes. The mean Knee Society knee score was 92.2. Eight-six percent of patients noted no or mild (occasional) pain at final follow-up. Three components have been retrieved for chronic sepsis. All were solidly fixed to bone with intact acrylic interfaces and extensive ingrowth. Osteointegrated bony interfaces were present around the smooth central stem. Hybrid fixation of tibial prosthetic components appears to be a viable concept.

Abstracts

From the AAHKS

Third

Annual

109

underwent a cemented total knee replacement. The average age at surgery was 69 years (range of 59-74 years) and the average period between patellectomy and total knee replacement was 7.5 years (range of 2-14 years). Eighteen knees had undergone patellectomy for a commmuted fracture while the remaining patellectomies had been performed for “chondromalacia or osteoarthritis.” In nine knees (Group A) a posterior stabilized implant (i.lsall-Berstein) was used. In 13 knees (Group B) a posterior cruciate retaining implant was chosen (RMC or Tricon-MI. while in the remaining two knees the posterior cruciate ablating Total Condylar prosthesis was used. All the surgical procedures were performed under general anesthesia. Ligament balancing and flexion and extension s”,~~~lequ,~~a’~enm~~a~ using intermedullary performed instrumentation. Cephalosporin was use in the peri-operative period for 48 hours. Coumadin was used for the first 7 days after surgery. Routine venography was not performed. Patients were evaluated pre and postoperatively using the Knee Society Rating System for both the knee score and function score. Preoperative scores were statistically similar in three groups. The results of a randomly selected group of patients from our database with osteoarthritis in whom a posterior stabilized prosthesis was used for a total knee replacement, but who had not had a prior patellectomy (Group Cl were compared to those in Group A. RESULTS: The mean pre op knee scores in Groups A, B were 45 and 47. The mean post op knee scores at 5 years after surgery were 89 and 67 respectively (p < ,001) The two patients who had a total condylar prosthesis implanted had a pre-operative mean score of 44 and a five year post operative knee score of 85. The mean total flexion in Groups A and B were 113 and 105 degrees respectively (p < .Ol). At five years after surgery all but one of the patients in Group B had antero-posterior instability at 90 degrees of flexion of > Icm, while only 1 patient in Group A had such instability. There were four knees in the series which had recurvatum at five years. All were in Group B. In the total series 7 knees had a pain score of < 30 points. Six of the seven patients had undergone more than three operative procedures prior to the patellectomy and all of these procedures had been performed for either chondromalacia or osteoarthritis. The mean post-operative knee score in the non patellectomy group that underwent a posterior stabilized prosthesis was 90, with a mean maximum flexion arc of 112 degrees. The percentage of knees in the control Group C able to ascend or descend stairs in a reciprocal manner was 67% while in Group A was 55%. SUMMARY: Total knee replacement using a posterior stabilized implant yields results in the post patellectomy group equal to that seen in primary total knee patients. In the post patellectomy patient attempted retention of the posterior cruciate ligament yielded inferior results both as related to pain relief, motion, flexion stability and stair climbing.

PAPER

Normal

Patella

of the thickest

Anatomy:

anterior-posterior

*26

--

Medial eccentricity dimension

B. Pace, MD Greenville, SC Aaron A. Hofmann, MD Salt Lake City, E. Jeff Kennedy, MD Sarasota Fl Kevin R. Kane. MD Salt Lake City. UT Thomas

TOTAL KNEE REPLACEMENT IN THE POST PATELLECTOMY PATIENT. Richard S. Laskin, MD, New York, NY.; George Paletta MD, New York, NY. INTRODUCTION: Total knee replacement is the most effective method presently available for the treatment of the patient with severe arthritis of the knee. Often, patients who are candidates for a knee replacement have undergone prior surgery on the joint and resulting in bone loss, scarring or changes in the pattern of motion. These may compromise the results of the knee replacement and may dictate the method that the surgery be performed and the choice of the type of implant. This study was undertaken to evaluate the results of knee replacement in patients who had undergone a prior patellectomy, either as the treatment of a severe fracture or for the alleviation of symptoms referable to chondromalacia patellae or osteoarthritis. MATERIALS AND METHODS: Twenty four osteoarthritic patients who had previously undergone a patellectomy and who then presented with severe degenerative knee disease,

Meeting

UT

In an attempt to quantify the eccentricity of the patella regarding the thickest anterior-posterior portion, 200 patellae were calibrated from the sunrise view x-rays. All x-rays were of patients on whom knee arthroplasty had been performed. Using a magnification marker and the OrthoGraphics, Inc. Orthoplan program, each patella was digitized

and

precise

measurements

made

regarding the relative medial-lateral position of the thickest anterior-posterior dimension. Only patellae with a convex contour were included. The average age was 66 and male and female