Lawrence D. Dorr

Rationale of the Knee Society clinical rating system.

A new total knee rating system has been developed by The Knee Society to provide an up-to-date more stringent evaluation form. The system is subdivided into a knee score that rates only the knee joint itself and a functional score that rates the patients ability to walk and climb stairs. The dual rating system eliminates the problem of declining knee scores associated with patient infirmity.

Impingement with total hip replacement.

Impingement is a cause of poor outcomes of prosthetic hip arthroplasty; it can lead to instability, accelerated wear, and unexplained pain. Impingement is influenced by prosthetic design, component position, biomechanical factors, and patient variables. Evidence linking impingement to dislocation and accelerated wear comes from implant retrieval studies. Operative principles that maximize an impingement-free range of motion include correct combined acetabular and femoral anteversion and an optimal head-neck ratio. Operative techniques for preventing impingement include medialization of the cup to avoid component impingement and restoration of hip offset and length to avoid osseous impingement.

Minimally invasive total hip arthroplasty development, early results, and a critical analysis

Hip replacement with use of small incisions has been practiced selectively by a few practitioners for many years, but only in the last several years has so-called minimally invasive hip replacement been widely introduced to the majority of orthopaedic surgeons. Minimally invasive hip replacement, in fact, is not a single type of surgery but rather is a family of operations designed to allow total hip replacement to be done through smaller incisions, potentially with less soft-tissue disruption. The three main methods involve a combination of a small incision and a posterior approach to the hip, a combination of a small incision and an anterior approach to the hip, or two small incisions performed with use of the Smith-Peterson interval for acetabular placement and the approach usually used for femoral intramedullary nailing for femoral component insertion. Minimally invasive total hip arthroplasty has created much controversy among orthopaedic surgeons and a great deal of publicity in the popular press. Advocates emphasize the potential for these methods to reduce soft-tissue trauma and thereby reduce operative blood loss, postoperative pain, and hospitalization time; speed the postoperative recovery; and improve the cosmetic appearance of the surgical scar. Advocates view minimally invasive total hip arthroplasty as a logical extension of less invasive methods that have revolutionized other fields, such as arthroscopy, laparoscopic cholecystectomy, and cardiac surgery, just to name a few. Those with reservations about minimally invasive total hip replacement point out that conventional hip replacement already provides excellent pain relief, functional improvement, and durability with a low complication rate. Skeptics are concerned that minimally invasive procedures introduce new potential problems related to reduced visualization at the time of the operation, such as implant malposition, neurovascular injury, poor implant fixation, or compromised long-term results. Advocates of minimally invasive methods believe that minimally invasive hip arthroplasty holds …

Total hip arthroplasty in protrusio acetabuli of rheumatoid arthritis.

Thirty-five total hip arthroplasties done in twenty-five patients with protrusio acetabuli secondary to rheumatoid arthritis were reviewed. There was an average follow-up of 4.3 years, with a range of three to seven years. The results were rated as excellent or good in 66 per cent, fair in 26 per cent, and poor in 8 per cent. Although 100 per cent demonstrated cementbone interface demarcation around the acetabular component, only 10 per cent showed progression of the line of demarcation to two millimeters and one had acetabular loosening with migration. Eight per cent showed femoral loosening or subsidence; 8 per cent, calcar resorption; and 6 per cent, a receding cortex with cystic changes. Twenty-three per cent had nonunion of the greater torchanter after trochanteric osteotomy. Type-III cement-bone interface demarcation was present around the acetabular component was positioned one centimeter superiorly or medially beyond the anatomical position, as estimated by the method described. In thirteen hips in which the acetabular component was positioned within five millimeters of the anatomical position, no Type-III demarcation was present. Better fixation and position of the acetabular component is achieved by the use of a bone graft or a special titanium perforated-sheet mesh, or both, or by an acetabular shell. The use of three wires improved trochanteric fixation.

Total Hip Arthroplasty with Use of the Metasul Metal-on-metal Articulation: Four to Seven-year Results*

Background: Total hip replacements with a metal-on-metal articulation were commonly used until the mid-1970s; most were then abandoned in favor of hip replacement with a metal-on-polyethylene articulation. The reason for this change was primarily early cup loosening, which was more prevalent with these metal-on-metal designs than it was with metal-on-polyethylene designs. In the late 1980s, a metal-on-metal design with improved clearance (adequate space between the femoral head and the acetabular articulation surface to allow fluid film lubrication and clearance of any debris from within this joint), metal hardness, and reproducible surfaces was introduced by Sulzer Orthopedics in Switzerland. Orthopaedic surgeons were interested in this Metasul articulation because the contribution of polyethylene wear particles to the failure of total hip replacements had become evident. This study was undertaken to review the clinical performance of this implant and to determine if early acetabular loosening or revision and wear and osteolysis were prevalent. Methods: Between 1991 and 1994, seventy patients (seventy hips) had a total hip replacement with the Metasul metal-on-metal articulation and a cemented Weber cup. Nine patients died less than four years after the replacement; none of these deaths were related to the operation. Five patients were not available for radiographic evaluation, but they were contacted and it was known that the hip was not painful and had not been revised. Fifty-six patients (fifty-six hips) had complete clinical and radiographic data four to 6.8 years after the operation, and they made up the study group. The patients were evaluated with use of the Harris hip score, a patient-self-assessment form, and radiographs. Results: At an average of 5.2 years (range, four to 6.8 years) after the operation, the average total Harris hip score for the fifty-three patients who did not have a revision was 89.6 points (range, 62 to 100 points). The average Harris pain score was 41.0 points (range, 30 to 44 points), and the average Harris limp score was 9.4 points (range, 5 to 11 points). One patient had revision of a loose cup, but there were no other loose acetabular components in the series. Two patients had revision of the acetabular component because of dislocation. No patient had a loose or revised femoral component. Therefore, the mechanical failure rate was one (2 percent) of fifty-six patients. Thirty-six of forty-seven patients who completed the patient-self-assessment form rated their result as excellent; seven, as very good; two, as good; one, as fair; and one, as poor. Wear could not be measured on radiographs because of the metal-on-metal articulation. No hip had radiographic evidence of acetabular osteolysis and two hips had calcar resorption, but there was no other radiographic evidence of focal osteolysis. Conclusions: Our four to seven-year experience with this articulation surface indicates that the clinical results are similar to those of total hip replacements with a metal-on-polyethylene articulation. We believe that the Metasul articulation may have a role in reducing the wear that occurs with total hip replacement. The Metasul articulation appears to be particularly indicated for more active patients. A historical comparison with the reports in the literature of which we are aware indicated that the hips in our study had a lower rate of acetabular revision and loosening than did those with previous metal-on-metal designs and that they had no more acetabular loosening or osteolysis than did those with metal-on-polyethylene articulations followed for an average of five years.

Clinical Performance of a Durasul Highly Cross-Linked Polyethylene Acetabular Liner for Total Hip Arthroplasty at Five Years

BACKGROUND Highly cross-linked polyethylene is currently the most common articulation surface used for total hip arthroplasty. The hypothesis of the present study was that the Durasul highly cross-linked polyethylene acetabular liner would have less wear at five years than would a conventional polyethylene liner used in association with the same total hip replacement system. METHODS Forty-three consecutive patients (fifty hips) underwent total hip replacement with an uncemented titanium porous-coated metal cup and a Durasul liner that was mated with a 28-mm cobalt-chromium femoral head. Thirty-one patients (thirty-seven hips) were followed for at least five years. Thirty-five other patients (thirty-seven hips) underwent total hip arthroplasty with the same system but with a conventional polyethylene liner, and these patients also were followed for five years. Clinical assessment was performed with use of the Harris hip score and a patient self-assessment examination. Radiographic analysis included measurements of acetabular component position, fixation, and osteolysis. Femoral head penetration of the Durasul liners was compared with that of the conventional liners. RESULTS The clinical results as determined on the basis of Harris hip scores and patient self-assessment examinations did not differ between the Durasul group and the control group. The mean bedding-in penetration was 0.054 +/- 0.07 mm for the Durasul group and 0.059 +/- 0.154 mm for the control group. The subsequent penetration, with elimination of the bedding-in wear, resulted in a linear wear rate of 0.029 +/- 0.02 mm per year for the Durasul group, compared with 0.065 +/- 0.03 mm per year for the control group (p < 0.005). The annual penetration at one and five years was 0.074 mm and 0.011 mm, respectively, for the Durasul group, compared with 0.151 mm and 0.04 mm, respectively, for the control group. CONCLUSIONS While the qualitative wear pattern of the highly cross-linked polyethylene liner was the same as that of the conventional polyethylene liner, the annual linear wear rate was 45% of that seen with the conventional polyethylene liner. Therefore, we believe that these early data support the continued use of this highly cross-linked polyethylene liner for total hip arthroplasty.

Long-term results of cemented total hip arthroplasty in patients 45 years old or younger. A 16-year follow-up study.

Forty-nine cemented total hip arthroplasties in patients younger than 45 years were reviewed, with an average follow-up period of 16.2 years. The results were compared with the same group previously reported at average follow-up periods of 4.5 and 9.2 years. Clinically satisfactory results were 27% at 16.2 years compared with 78% at 4.5 years and 58% at 9.2 years. The revision rate increased from 12% at 4.5 years to 33% at 9.2 years to 67% in this study. The revision rate for patients younger than 30 at the time of the index arthroplasty was 82% compared with 56% for those over 30. Impending failure was present in 81% of the 16 unrevised hips compared with 56% at 9.2 years and 29% at 4.5 years. Patients younger than 30, in Charnley category A or B, and with a diagnosis of osteonecrosis or osteoarthritis had the poorest clinical results. As in the previous two studies, the best results were obtained in category C patients who were over 30 years of age with inflammatory collagen disease. The purpose of this study is to report the long-term (average, 16.2 years) follow-up results of patients under the age of 45 who underwent cemented total hip arthroplasty at Rancho Los Amigos Medical Center between 1972 and 1978. The 4.5-year and 9.2-year results form the basis for comparison.

Early pain relief and function after posterior minimally invasive and conventional total hip arthroplasty. A prospective, randomized, blinded study.

BACKGROUND Few prospective randomized studies have demonstrated benefits of minimally invasive total hip arthroplasty when compared with conventional total hip arthroplasty. We hypothesized that patients treated with a posterior mini-incision would have better results than those treated with a posterior long incision with regard to the achievement of established goals for pain relief and functional recovery permitting hospital discharge by the second postoperative day. METHODS Sixty of 231 eligible patients were randomized (with thirty in each group) to have a total hip arthroplasty performed through either a posterior mini-incision (10 +/- 2 cm) or a traditional long incision (20 +/- 2 cm). After completion of the total hip arthroplasty, the mini-incision group underwent extension of the skin incision to 20 cm. Patients were evaluated on the basis of self-determined pain scores, requirements for pain medicine, need for assistive gait devices, and time until discharge. Gait analysis provided objective functional assessment. RESULTS The average hospital stay was 63.2 +/- 13.3 hours in the mini-incision group and 73.6 +/- 23.5 hours in the long-incision group (p = 0.04). More patients with a mini-incision were discharged by the second postoperative day (p = 0.003) and more were using just a single assistive device at the time of discharge (p = 0.005). As scored on a verbal analog scale of 0 to 10 points, patients with a mini-incision had less pain on each postoperative day and the pain score remained significantly lower at the time of discharge (mean, 2.2 +/- 1.0 points compared with 3.1 +/- 0.9 points in the long-incision group; p = 0.002). After hospital discharge, there were no clinical differences in pain or function between the two groups of patients. CONCLUSIONS Compared with conventional total hip arthroplasty performed through a posterior incision, posterior minimally invasive total hip arthroplasty resulted in better early pain control, earlier discharge to home, and less use of assistive devices. Subsequent evaluations at six weeks and three months showed equivalency between the clinical results in the two groups. LEVEL OF EVIDENCE Therapeutic Level I.

Complications with hydroxyapatite particulate separation in total hip arthroplasty

This study reports on the results of the implant and tissue analysis of clinically retrieved hydroxyapatite (HA)-coated implants. Five of the patients with fixed HA-coated stems had been clinically diagnosed with osteolysis. The semiquantitative histologic grading in these patients showed HA, polyethylene, and metal particles were all present (Grade 3+) in the osteolytic regions of the periprosthetic tissue. Additionally, inflammatory cells (Grade 3+) were present in these regions. Back-scattered electron (BSE) and correlated elemental analysis showed HA particulate was present in the polyethylene inserts. The HA could be distinguished from bone chips in the polyethylene based on morphology and anatomic number gray level differences. This study was limited in that no clinical results of particular HA-coated implant series were reported. Careful follow-up care in patients with coated devices is recommended.

Functional comparison of posterior cruciate-retained versus cruciate-sacrificed total knee arthroplasty.

Gait of 11 patients with bilateral paired posterior cruciate-retaining and cruciate-sacrificing total knee arthroplasties (TKA) was studied preoperatively and two years postoperatively on walking and stair climbing. Five-year clinical and roentgenographic examinations were included in the study. Differences between the two prostheses were noted both in level walking and in stair climbing. On level walking, cruciate-sacrificed TKA had more flexion in loading response and increased flexion and varus moments with increased muscle activity of quadriceps and biceps femoris. Abnormal gaits common to both types of knee were decreased flexion in stance and decreased single-limb stance. Both knees had a stiff-legged gait during stance. On stairs, the cruciate-sacrificed TKA substituted soleus muscle activity for knee stability. The single-limb stance and range of motion were similar for both knees. In clinical terms, the cruciate-sacrificed TKA is less efficient and has greater medial loading and higher joint reaction forces that may affect durability of the prosthesis. The five-year knee scores, patient satisfaction, and roentgenographic examinations were equal for both sets of knees.