Uncemented Total Hip Arthroplasty Utilizing A Proximally Stress- Loaded Femoral Stem With A Dual-Finned Acetabular Component: A Short-Term Followup

David Brys, MD, Sandra Chadwick, RN, Brys Orthopedic Clinic, Warren, Ohio

Introduction – Many total hip designs in today’s marketplace do not take advantage of the known force vectors present in the femur.(Figure 1) Fully porous coated stems have been shown to transfer stresses distally, resulting in increased proximal bone resorption.(Figure 2) Collarless stems cannot adequately replace the longitudinal forces seen in the femur prior to total hip arthroplasty. (Figure 3a-b) This forces a stable femoral stem to rely upon fixation with artificially created force vectors. This study documents the short-term clinical results with the BioPro PSL Hip System, which was designed to address the aforementioned issues.

Conclusion – This clinical followup is the first to report outcomes with the BioPro PSL System, as well as a magnesia-stabilized zirconia ceramic head. The results suggest this hip system can be effectively used to reduce patient pain and successfully restore joint functionality.


Horizontal Platform Supported Hip Replacement

James W. Pritchett, MD*; and Charles O. Townley, MD†

Abstract: The cementless horizontal platform supported femoral component for hip replacement was designed to provide physiologic stress loading of the proximal femur after hip replacement. The goal is to extend pain-free implant survival by reducing periprosthetic bone resorption and to provide improved hip function and many years of relief from hip pain. A total hip replacement using this prosthesis was done in 334 consecutive nonselective hips in 322 patients. The mean age of the patients at the time of total hip replacement was 69 years (range, 29–89 years). Thirty-two patients (34 hips) were lost to followup and 81 patients (83 hips) died less than 10 years postoperatively. The remaining 209 patients (217 hips) were followed up for a minimum of 10 years (maximum, 14 years). There were six revisions of the femoral prosthesis. Three (1.8%) were revised for loosening, two were revised for femoral fracture, and one was revised for unexplained pain. The rate of stem survival was 0.97 ± 0.02 (mean and standard error). There were 209 (96%) hips with excellent or good results. Seven (3%) patients had osteolytic changes develop. Radiographic evidence of diminished bone density in the proximal femur was seen in 34 hips (16%). The clinical results are comparable with other reported results for cementless hip replacements at 10 years.


Femoral Bone Loss Following Hip Replacement: A Comparative Study

James W. Pritchett, MD

Abstract: Fifty Femoral stems of 5 different types were compared with respect to bone retention in the proximal femur at least 3 years after implantation. Dual energy xray absorptiometry scans were used to compare bone mineral density in the medial neck of the replaced hip with that of the other hip where surgery had not been performed. Bone mineral density declined on average of 57% with the cemented straight stem Mueller prosthesis and 34% for the uncemented Anatomic Medullary Locking prosthesis. For the cemented Harris Pre-coat prosthesis, the decline in bone mineral density was 43%. Two uncemented implants with horizontal platform-type collars showed an average decline in bone mineral density of 8% and 14%. Clinically, all the stems functioned well, and excellent implant insertion technique had been used. The decline in bone mineral density was evident on plain radiographs. The decrease in bone mineral density paralleled the known decrease in the medial neck strain. This study suggests that more proximal bone will be maintained by implants that load the proximal femur in as physiologic a fashion as possible.


Leimin Chen and Thomas J. Claffey, Horizontal platform supported total hip replacement

Chin Med J 1998; 111(12):1094-1098

Objective – To investigate the effect of horizontal platform supported (HPS) prosthesis on cementless total hip replacement for surgical treatment of arthritis in a long-term follow-up study.

Conclusion – The findings suggest that the clinical and radiographic results after cementless total hip replacement for primary hip arthroplasty may be favourably influenced by the use of the proximal stress loaded HPS femoral component.


The Importance of the Stem Geometry, Porous Coating, and Collar Angle of Femoral Hip Prosthesis on the Stress Distribution in the Human Femur

J.P. Collier, F. Kennedy, M. Mayor, C. Townley, E. Amoakuh, Thayer School of Engineering, Dartmouth College, Hanover, NH 03755

Introduction – Recent investigations of the failure of femoral hip prostheses have demonstrated that they are often accompanied by bone reorption in the medialcalcar area and stem loosening. Studies by R. Crowninshield, and Oh and Harris, using strain measurements of cadaver bones have indicated that prosthesis implantation commonly results in a reduction in the longitudinal strain in the calcar area by 30-40% from the normal intact femur. In those studies, both ends of the cadaver femur were firmly fixed and a load was applied to simulate the anatomical condition. The loading of the femur therefore, was directly affected by the presence of lateral forces and this may radically reduce and alter the stress and strain.

Conclusions – These results suggest that the bone remodeling, now often seen after hip arthroplasty, may in large part be related to stress induced bone formation and stress shielding resulting in bone resorption. These changes may be preventable as predicted by the analysis described.


Wolff’s law fundamental to implant surgery

Bill Edelman, Orthopedics Today, page 16, October 1990

PORT HURON, Mich – Long-term stability of a total hip prosthesis “requires an implant design and a fixation technique that simulate the normal transmission of weight-bearing forces through the prosthesis to the supporting bone structures,” said Charles O. Townley, MD, of Port Huron. Basic concepts are simple. More than a century ago, Julius Wolff determined that bone develops mathematically, taking the structure best suited to cope with the forces acting upon it. Although this idea has been refined and modified over the succeeding decades, Wolff’s Law remains a basic tenet that Dr. Townley finds fundamental to prosthetic joint replacement.

Ceramic Articulation in Surface Replacement Arthroplasty

BioPro Technical Bulletin

Introduction – Surface replacement arthroplasty of the hip has been an effective conservative treatment for many patients who would otherwise be candidates for conventional total hip replacement. This technical communication will briefly describe the surgical technique and reports a short term clinical followup on the BioPro ceramic surface replacement prosthesis, formerly known as the TARA.

Conclusion – This procedure is highly technique dependent. Proper education on head resection (superior and circumferential), size selection, and cementing is essential to ensure a successful procedure. When performed correctly, this procedure is presented as an excellent conservative treatment option for hip replacement candidates.


Femoral Surface Strain Analysis: A Comparison Between a Cup Arthroplasty and Conventional Long-Stem Prostheses

Hazelwood, S.J., Rodrigo, J.J., Sharkey, N.A., Raiszadeh, K., Orthopaedic Research Laboratory, University of Calfiornia, Davis

Introduction – The effects of stress shielding have been the subject of much research in recent years. It is recognized that the transmission of load from the implant to the bone is one of the most important factors in determining the longevity of femoral prostheses

[1]. Bone resorption of the proximal femur, believed to be the normal remodeling response die to the shielding of bone from stress by the femoral component, has been attributed as the major cause of several long-term failures of the implant and surrounding bone [2]. This is particularly a problem for younger hip implant recipients, who tend to be more active and need an implant which lasts longer than normal. With the recent increase in the number of young patients receiving hip implants, an interest has been rekindled among several orthopaedists to return to the femoral “cup” type of arthroplasty, whose design is such that bone resorption due to stress shielding may be prevented. Specifically, the design simulates the actual femur head size and preserves a majority of the original bone stock, which will theoretically approximate the normal transmission of stresses to the bone. To quantitatively determine which femur-implant construct produces a more natural strain distribution of the femur, a femoral surface strain analysis was performed comparing a cup arthroplasty with both a cemented and a cementless conventional long-stem prosthesis.


Surface Replacement Hemiarthroplasty for the Treatment of Osteonecrosis of the Femoral Head

Marc W. Hungerford, MD, Michael A. Mont, MD, Richard Scott, MD, Christopher Fiore, MD, David S. Hungerford, MD, Kenneth A. Krackow, MD, Copyright 1998 by The Journal of Bone and Joint Surgery, Inc.

Abstract: We reviewed the results of thirty-three femoral resurfacing procedures in twenty-five patients who had stage-III or early stage-IV osteonecrosis of the femoral head according to the classification system of Ficat and Arlet. There were no perioperative complications. Thirty hip prostheses (91 percent) survived for a minimum of five years. At a mean of 10.5 years (range, four to fourteen years) postoperatively, sixteen (62 percent) of the twenty-six hips with stage-III disease had a good or excellent Harris hip score. Four of the seven hips with stage-IV disease did not have or need a total hip arthroplasty. Overall, twenty hips (61 percent) had a good or excellent result according to the scoring system of Harris, and thirteen (39 percent) had a fair or poor result and subsequently had or needed a total hip arthroplasty. The mean interval between the hemiarthroplasty and the total hip arthroplasty was sixty months (range, thirty-six to 136 months). These thirteen hips all had a successful clinical result (a Harris hip score of at least 80 points) at a mean of thirty months (range, twenty-four to seventy-two months) after the total hip arthroplasty.

The results of the present study suggest that resurfacing of the femoral head can be a successful interim procedure for the management of patients who have Ficat and Arlet stage-III or early stage-IV disease with a large lesion that is not amenable to other treatment options except total hip arthroplasty.


Complications in Total Hip Replacement: Etiology, Prevention and the Role of a Ceramic Articulation

Charles O. Townley, MD, Townley Orthopedic Clinic, Port Huron, Michigan

Introduction – In the interest of providing background information for engineers and other reviewers who may not be familiar with the ramifications of this specialized subject, this discourse will be introduced by identifying the various methods of hip replacement and modes of fixation of the prosthetic implants.


Hemi and Total Articular Replacement Arthroplasty of the Hip with the Fixed Femoral Cup

Charles O. Townley, MD, Orthopedic Clinics of North America – Vol 13, No 4, October 1982

Introduction: The original major objectives of the design were to preserve bone stock, maintain the normal anatomy and mechanics of the hip joint, and to approximate the normal in-vivo transmission of stress to the supporting femoral bone. Although the shell-like articular surfacing provided by the Smith-Peterson cup would seem ideally suited to these requirements, the high incidence of failure associated with femoral head degradation led to its abandonment in favor of excisional replacement. This radical approach subsequently became “conventional” practice.


Hip Joint Resurfacing

James W. Pritchett, MD and Charles O. Townley, MD

ABSTRACT: Hip joint resurfacing is an attractive concept because it preserves rather than removes the femoral head and neck. With a more natural arthroplasty there is the promise of better function, and a less difficult revision if it is needed later. This report will be the first long term report on the results of total hip resurfacing. 445 patients (561 hips) were followed for a minimum of twenty years. Only 23 patients were lost to follow up. The average age at surgery was 52. More than 84% percent of patients were followed until their death. A femoral prosthesis with a small curved stem was used in all patients. Three different types of acetabular reconstruction were employed. In the first cases, before polyethylene was available, polyurethane, polyacetal and nylon were used. Next, metal-on-metal was used. Polyethylene either secured with cement or as the liner of a two piece porous-coated implant was next. The short term results were excellent with all acetabular combinations. The long term results were not with the exception of metal-on-metal. None of the 121 patients (133 hips) who received a metal-on-metal prosthesis experienced failure or a complication. The failure rate with cemented polyethylene at 20 years was 41%. Surgical complications were infrequent. Hip resurfacing using a metal-onmetal articulation with a stemmed femoral component is a durable and successful procedure. It is technically demanding.



The Role of Unicompartmental Knee Arthroplasty

Todd D. Schwartz, Raman Battish, and Paul A. Lotke, Seminars in Arthroplasty, VOL 11, No 4 (October), 2000: pp 241-246

Abstract: This report provides a current overview of unicompartmental knee arthroplasty – indications, technique, complications, and recent published long-term follow-up. Recent long-term survivorship studies, with the use of modern prosthetic designs, show good-to-excellent results in 90% or more cases at 10 years. Proper surgical technique and patient selection are required to optimize outcome. If appropriate criteria are met, the results of unicompartmental knee arthroplasty compare favorably with total knee arthroplasty and proximal tibial osteotomy, and the procedure remains a viable alternative in those patients with unicompartmental gonarthrosis.


Modern Unicompartmental Knee Arthroplasty with Cement: A Three to Ten-Year Follow-up Study

Jean-Noel A. Argenson, MD, Yamina Chevrol-Benkeddache, MD, and Jean-Manuel Aubaniac, MD, The Aix-Marseille University

Background: Unicompartmental arthroplasty is a treatment alternative when only one compartment of the knee is affected with arthritis, but the reported results of this procedure have been variable. The purpose of the present study was to evaluate the results of a modern unicompartmental knee arthroplasty performed with use of a cemented metal-backed prosthesis and surgical instrumentation comparable with that used for total knee replacement.

Conclusions: A modern unicompartmental knee arthroplasty is a valid alternative for patients with unicompartmental tibiofemoral noninflammatory disease. The patient selection must be strict with regard to the status of the patellofemoral joint. The preoperative planning includes stress radiographs to assess the correction of the deformity and the status of the uninvolved compartment. Continued long-term follow-up is necessary to evaluate long-term polyethylene wear.


ACL retention offers good results in TKA: Longterm bilateral study favors knees with both ligaments saved

Lee Beadling, Orthopedics Today, October, 1995, Vol 15, No 10

SAN DIEGO – A two to five-year follow-up study by Seattle surgeon indicates that retaining both the ACL and the PCL in unconstrained total knee arthroplasty may result in greater patient satisfaction, less effusion about the knee, and cost savings.


Anterior Cruciate-retaining Total Knee Arthroplasty

James W. Pritchett, MD, The Journal of Arthroplasty Vol 11 No 2 1996

Abstract: Fifty patients underwent bilateral total knee arthroplasty retaining both cruciate ligaments on one side and only the posterior cruciate ligament on the other. Patients were questioned about pain, instability, “feel,” and ability to climb stairs. Seventy percent of patients stated that their anterior and posterior cruciate-retaining knee was their better knee overall. Ten percent stated that their posterior cruciate-only knee was better. Twenty percent could find no difference. There were no meaningful differences in inpatient care, physical therapy requirements, strength, range of motion, or component positioning. Fourteen patients handled stairs using each knee equally. Twenty-nine climbed stairs leading with the anterior and posterior cruciate-retaining knee and seven patients led with the posterior cruciate-only knee. Complaints of clunks, pops, and clicks occurred in 11 patients with posterior cruciate-only knee arthroplasties and in 4 patients retaining both anterior and posterior cruciate ligaments. Retaining the anterior cruciate ligament can provide a knee that subjectively “feels” better.


The Cruciate Ligaments in Total Knee Arthroplasty: A Kinematic Analysis of 2 Total Knee Arthroplasties

James B. Stiehl, MD, Richard D. Komistek, PhD, Jean-Marie Cloutier, MD, and Douglas A. Dennis, MD, The Journal of Arthroplasty Vol. 15 No. 5 2000

Abstract: In vivo weight-bearing fluoroscopic kinematic analysis using an interactive model fitting technique with 3-dimensional computer-aided design solid models was done using 16 anterior and posterior (bicruciate)-sparing and 6 posterior cruciate-sparing total knee arthroplasties (TKAs). All patients had a satisfactory clinical result with a minimum of 12 months’ follow-up. The femorotibial contact position of TKAs started posterior to the midline in extension. Bicruciate TKAs revealed gradual posterior femoral rollback and limited anterior-posterior translation but remained posterior to the sagittal plane midline in all positions. Posterior cruciate-sparing TKAs began significantly posterior in extension, demonstrated progressive anterior translation with flexion, and had exaggerated medial condyle translation on deep knee bend. The posterior cruciate-retaining TKAs of this study had the most abnormal kinematic performance.


Total Knee Arthroplasty: A Personal Retrospective and Prospective Review

Charles O. Townley, MD

Introduction: The author’s current concepts of total knee arthroplasty evolved from the design and subsequent 20 years’ experience with a metallic tibial plate in more than 170 knees between 1953 and 1972. The rationale for this resurfacing device and, later on, for the development of the author’s total knee replacement ensemble was based on certain basic principles that were directed to the preservation of bone stock and the reconstitution of the normal knee joint modalities. Sixteen subsequent years of personal experience in the implantation of more than 1700 total knee replacements commencing in1972, using both cemented and uncemented fixation technique, have clearly established the direct relationship between the successful results and the degree of precision in the implementation of correct anatomic principles.

Articular-Plate Replacement Arthroplasty for the Knee Joint

C.O. Townley, MD, Clinical Orthopaedics No. 36

Introduction: Many knees, unresponsive to nonoperative conservative measures, respond favorably to debridement procedures, patellectomy, etc. However, many mechanically disturbed knees with severe varus or valgus instability or total loss of the cartilaginous articular barrier are persistently painful in spite of such procedures. The rheumatoid arthritic knee with intractable and debilitating acute symptomatology, not responding to conservative medical care, is not amenable to the usual surgical procedures. In these instances, the orthopaedic surgeon is faced with the alternative of continued, ineffectual conservative measures, arthroplasty or arthrodesis.

Conclusions: While a small percentage of patients with knee joint difficulty require this radical surgery, on the basis of this short-term report, the results of this procedure as a means toward relief of pain, with retention of adequate and useful motion, are encouraging. The design of the plate allows a long-lasting, anatomically contoured, articular surface, which accommodates the paraboloid are of motion of the knee and preserves or restores mechanical stability. The procedure is proposed as an adjunct to existing, more conservative methods and is not indicated until other more conservative means of treatment have failed.


Total Knee Replacement

TOWNLEY, CHARLES; HILL, LESLIE, AJN, American Journal of Nursing. 74(9):1612-1617, September 1974.
Abstract: Close approximation of the prosthesis to anatomical contours and preservation of strategic ligaments during implantation are the secrets of success with this procedure.

The Anatomic Total Knee Resurfacing Arthroplasty

Charles O. Townley, MD, Clinical Orthopaedics, January-February, 1985, Volume 182

Introduction: The long-term results of total knee arthroplasty are largely dependent on the degree to which the implants and the technique for their insertion duplicate the normal joint anatomy, mechanics, and kinematics. Aberrations in these modalities, occasioned by technical malalignment of the joint or by nonanatomic designing, sizing, or positioning of the implants, are the predominant causes of postoperative limitation of motion and loosening of the implants. Although inadequacies in the bonding effect of cement and in the structural strength of polyethylene have been cited as contributing factors in the incidence of loosening of the tibial component, this complication occurred in less than 2% of 532 cemented Anatomic Total Knee (ATK) replacements that were available for review at a follow-up period of two to 11 years. The long-term follow-up results, based on pain relief, motion, and level of activity, were judged excellent or good in 89% of the knees. Problems related to the patella and loosening of the tibial component were the predominant mechanical complications that required revision. The incidence of loosening was routinely related to technical malalignment of the knee joint or the prosthesis. However, experimental and recent clinical studies indicate that porous-surfaced implants may provide a more durable and long-lasting mode of stabilization. Except for the adaptation of the implants to the porous-coated, noncemented technique, the ATK arthroplasty ensemble has remained essentially unchanged from the original 1972 design.


The Anatomic Total Knee: Instrumentation and Alignment Technique

C.O. Townley, MD, Papers of the First Scientific Meeting of the Knee Society (1984)

Introduction: The severe functional demands placed on the knee are successfully countered in the normal joint by a finely tuned biomechanical arrangement that maintains symmetrical loading of the articular surfaces under widely varying conditions of stress and motion. In the normal arrangement the universal distribution of surface stresses provided by the intrajoint behavior of the synovial fluid and articular cartilage is augmented by anatomical mechanical modalities that maintain the transverse plane of the joint in a compressive, nonshearing position to the mean projection of weight-bearing forces. Aberrations in the normal joint mechanics, occasioned by varus or valgus angular deformities or nonanatomical alignment of the joint surfaces in the transverse plane, are major precipitating factors in the pathogenesis of gonarthrosis. The excessive and abnormally directed stresses induced by similar mechanical disorders following total knee replacement can be expected to have, if anything, an even greater disruptive arthritic effect on the insensitive, Charcot-like implants in the form of deformation or loosening. For optimal clinical results, therefore, a basic understanding of the mechanics and functional behavior of the knee joint must be augmented by instrumentation and surgical technique that will reproduce, within reasonable imits, anatomical valgus alignment of the joint and the normal, compression-resistant position of the implants to the projection of weight-bearing forces in the transverse plane.