Twenty-Five-Years and Greater, Results After Nonmodular Cemented Total Knee Arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) has been shown to be very successful with long-term follow-ups. But there are no reports showing prosthesis survival at 25-30 years. Here, we report the outcomes for 25-30 years using the Anatomic Graduated Component (Biomet, Warsaw, IN) TKA and elucidate the etiology and cause of failure of the components. METHODS: We reviewed the outcomes of 5649 primary total knee arthroplasties for 25-30 years using the Anatomic Graduated Component. Statistical analysis was performed by the Kaplan-Meier survival analysis. Clinical outcomes included the Knee Society Score and standardized radiographs to check for loosening of the implants. The reason for revision surgery was reviewed retrospectively. We compared our results with those at another institution with similar long-term follow-up. RESULTS: There were 112 failures, 48 with aseptic loosening and 25 with instability for an overall prosthesis survival rate of 94.2% at 25 years and 92.4% at 30 years follow-up. In the third decade after TKA, patients are substantially more likely to experience death than experience a failing prosthesis, with a 3811% greater risk of dying relative to failing (Risk ratio = 38.1, Odds ratio = 56.7, P < .0001). CONCLUSION: There was a greater risk of dying than failing over time. The primary reason for revision knee surgery was due to aseptic loosening of the prosthesis followed by instability.

Twenty-year followup of an uncemented stem in primary THA.

BACKGROUND: Uncemented stems have been used in THA for well over two decades, but there are relatively few studies reporting on the results after 20 years. QUESTIONS/PURPOSES: The purpose of this study was to evaluate at a minimum followup of 20 years (1) hip scores; (2) radiographic findings, including stem fixation and osteolysis; (3) reoperations; and (4) survivorship free from aseptic loosening in a group of patients who underwent primary THA using a proximally porous-coated, plasma-sprayed, straight-stemmed, titanium-alloy femoral component. METHODS: Between 1987 and 1993, we performed 1517 primary THAs, of which 447 were cementless, and 157 used the implant under study here (representing 10% of the THAs during the period in question). General indications for the use of the study stem included (1) younger age with relatively stronger bone (average age 55 years in this study); (2) patients not involved in another study protocol (as were the 278 other cementless hips implanted during this time); and (3) patients who, at the surgeon's discretion, would be compliant with protected weightbearing. Of those, 111 were available for followup at a minimum of 20 years (mean, 20 years), whereas 36 had died and nine (6%) were lost to followup or declined participation. The primary diagnosis was osteoarthritis in 77 hips (69%). The mean age at operation was 55 years. The clinical result was evaluated on the basis of the Harris hip score. Radiographic analysis was performed at each followup visit for distal cortical hypertrophy, spot welds, radiolucencies, stem subsidence, varus or valgus shift, osteolysis, and femoral component loosening. Kaplan-Meier analysis was performed to evaluate the survival of the femoral component. RESULTS: The mean Harris hip score improved from 46 points to 87 points (of a possible 100 points) at the most recent followup. All hips had evidence of proximal femoral remodeling consistent with osseous ingrowth. Femoral osteolyis was seen in 22 hips (20%). One stem was revised as a result of a periprosthetic fracture. No femoral component had evidence of loosening, and none was revised. Thirty-three acetabular components (30%) were revised. CONCLUSIONS: This femoral component provided durable long-term fixation for over two decades after THA. The porous stem geometry is still in use today and will continue to be studied into the third decade of use. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Use of screws and cement in revision TKA with primary or revision specific prosthesis with up to 17 years followup.

The purpose of this study was to investigate the use for screws and cement, and primary and revision specific prosthesis for revision TKA. Between July 1989 and February 2010, 839 consecutive revision TKAs were performed, with 609 knees meeting inclusion criteria. At 17 years followup, Kaplan-Meier survivorship was 0.9859 for revision specific prosthesis with screws and cement, 0.9848 for revision prosthesis with no screws, 0.9118 for primary prosthesis with screws, and 0.9424 for primary prosthesis with no screws. Revision TKAs using screws had greater defects (P<.0001). Use of revision prosthesis along with screws and cement to correct largely defective revision TKAs is highly recommended.

Use of screws and cement in primary TKA with up to 20 years follow-up.

The purpose of this study was to investigate screws and cement for large tibial bone defects during primary TKA. Of 14,686 consecutive primary TKAs performed between December 1988 and February 2010, 256 received screws and cement for tibial defects. Cox regression was used for the analysis. 20-year survival probability was 0.9897 (screws) and 0.9339 (no screws) (P = .4225 log-rank). Tibial bone condition was significantly worse in knees receiving screws (P < .0001) with 73.0% having defects in the screws group and 3.4% (P < .0001) for non-screws. Radiolucency appeared in 13.7% (screws) and 6.4% (no screws) postoperatively. Screws were $137 each, wedges $910 to $2240. Knees with tibial defects and screws performed similarly if not better than knees without defects at substantially lower cost than alternatives.

Pain relief and functional improvement remain 20 years after knee arthroplasty.

BACKGROUND: TKA provides demonstrable pain relief and improved health-related quality of life. Yet, a decline in physical function may occur over the long term despite the absence of implant-related problems. QUESTIONS/PURPOSES: (1) Does pain relief diminish over 20 years after TKA? (2) Does function decline over 20 years in terms of Knee Society function, knee, and walking scores? And (3) what is the patient-reported activity level at most recent followup? PATIENTS AND METHODS: We retrospectively identified 1471 patients with 1757 primary cruciate-retaining TKAs implanted between 1975 and 1989 and identified 128 living patients (8.7%) with 171 TKAs. Ninety-three patients were women. We determined Knee Society scores prospectively and UCLA scores retrospectively. Minimum followup was 20 years (average, 21.1 years; range, 20-27 years). Average age at last followup was 82.3 years (range, 45-103 years). Of the 128 patients, 66 (73 TKAs) died after 20-year followup. RESULTS: Pain scores did not diminish over time (average, 49; range, 20-50). Average knee score was 78 (range, 39-97). Function, stair, and walking scores diminished over time. Average function score was 70 (range, 5-100), primarily due to an average stair score of 35 (range, 0-50); average walking score was 37 (range, 10-50). All but two patients (two TKAs) could negotiate stairs; 95 patients (124 TKAs) could walk at least five blocks; three patients (three TKAs) were housebound. Of the 62 patients still living (98 TKAs), the average UCLA activity score was 8.3 (range, 5-10). CONCLUSIONS: Although aging may cause a gradual decline in physical activity, an improved functional capacity and activity level continue 20 years or more after TKA.

Low incidence of groin pain and early failure with large metal articulation total hip arthroplasty.

BACKGROUND: Large-diameter metal-on-metal articulations reportedly improve stability and wear in THAs. However, some reports suggest some patients have unexplained hip and early failures with these implants. Thus, the potential benefits may be offset by these concerns. However, the incidence of these problems is not clearly established. QUESTIONS/PURPOSES: We therefore assessed hip pain, function, osteolysis, and complications in patients with large-diameter metal-on-metal THA. PATIENTS AND METHODS: We retrospectively reviewed 611 patients who had 681 large-diameter metal-on-metal THAs with the same cup and head design. The average age at operation was 62 years, 53% of the THAs were in men, and the average body mass index was 32 kg/m(2). The diagnosis was osteoarthritis in 92% of the THAs. The minimum followup was 24 months (mean, 37 months; range, 24-60 months). RESULTS: Nine of the 611 patients (1.5%) experienced moderate or severe pain in the hip region that we considered to be coming from an extraarticular source in each case. Harris hip scores for pain averaged 42 points. Total Harris hip scores averaged 93 points. Cup abduction averaged 42°, and cup anteversion averaged 26°. There were no infections. Three cups (0.4%) were considered radiographically loose. All were secondary to inadequate seating of the shell. CONCLUSION: Our observations suggest with this implant the concerns of higher incidences of groin pain, early failures, and adverse tissue reactions were not confirmed. Early successes or failures with large-diameter metal-on-metal articulations may be implant specific. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Acetabular UHMWPE survival and wear changes with different manufacturing techniques.

BACKGROUND: Polyethylene wear may be affected by the type of polyethylene resin, manufacturing technique, degree of thermal stabilization, and sterilization technique. QUESTIONS/PURPOSES: We therefore compared femoral head penetration into the PE and cup survival using the same cup system with different PE resins, manufacturing, and sterilization techniques. METHODS: Our study group consisted of 1912 THAs performed using the same uncemented cup and identical 28-mm cobalt-chrome heads. The polyethylene varied as follows: Group 1 (94 cups), GUR 4150 resin, ram-extruded, sterilized in air, no barrier packaging; Group 2 (74 cups), same as Group 1 but sterilized in argon; Group 3 (75 cups), Himont 1900 resin, compression-molded bar stock, sterilized in argon, no barrier packaging; Group 4 (620 cups), same as Group 3 except with barrier packing; Group 5 (711 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon gas with barrier packaging; and Group 6 (338 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon with barrier packaging, irradiated with 50 kGy, heated below melting temperature, machined, and finally placed in nonbarrier packaging with gas plasma sterilization. Minimum followup was 2 years (average, 7 years; range, 2-17 years). RESULTS: Femoral head penetration averaged 0.05 mm per year for Groups 5 and 6 and was substantially lower than for Groups 1 to 4. Cup survival was higher at seven years in Groups 3, 4, and 5, and at 10 years in group 4 when compared to groups 1, 2, and 3. CONCLUSIONS: We observed lower FHP rates and higher cup survival with polyethylene machined from direct compression-molded bar stock, sterilized in argon gas, with barrier packaging. LEVEL OF EVIDENCE: Level III Therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

"Thicker" polyethylene bearings are associated with higher failure rates in primary total knee arthroplasty.

"Thin" modular polyethylene bearings have previously been associated with failure from wear. This study examined the influence of polyethylene thickness on survivorship in primary total knee arthroplasty (TKA). Do "thinner" or "thicker" bearings fail more? Six thousand seventy primary TKAs with a single implant design were reviewed. The failure rate in knees with bearings 14 mm or less was 0.7%, whereas the failure rate of knees with bearings 16 mm or greater was 2.3% (P < .0001; hazard ratio, 3.2). No knee was revised for polyethylene wear. Thicker bearings did not directly cause failure, but factors that lead to the insertion of a thicker bearing such as a deeper tibial resection and ligament imbalance may contribute to the observed increased failure. The significant influence of this often-unrecognized surgical variable has not been previously reported and must be carefully considered during TKA.

High preoperative range of motion is a significant risk factor for dislocation in primary total hip arthroplasty.

Dislocation after total hip arthroplasty (THA) is multifactorial and is dependent on surgical, implant, and patient factors. We hypothesized that high preoperative hip range of motion is an important variable contributing to instability after THA. We retrospectively reviewed 3379 THAs performed during a 21-year period. Average follow-up was 6.6 years. We examined the effect of surgical approach, femoral head size, and preoperative range of motion on dislocation rates. Patients with a posterior approach and 115 degrees or greater of combined preoperative flexion, adduction, and internal rotation dislocated at a significantly higher frequency than those with less than 115 degrees of combined motion (odds ratio, 1.9; P = .007). High preoperative motion in conjunction with a posterior approach and femoral head size less than 32 mm had the highest dislocation rate in our sample (5.9%). Preoperative range of motion is an important variable that should be taken into consideration during operative planning to help reduce the risk of dislocation.

Predicting patellar failure after total knee arthroplasty.

UNLABELLED: We identified patient and surgeon factors associated with patellar component failure in a series of 8530 TKAs performed in 5640 patients using the same posterior cruciate ligament-retaining TKA with all-polyethylene patellar components between January 1983 and December 2003. Patellar failure was defined as loosening, fracture, or patellar revision. All infections were excluded. Statistical analysis using Kaplan-Meier and Cox regression was used to determine the risk of patellar failure. Followup averaged 7.0 years (range, 2-22 years). Patellar component loosening occurred in 4.8% of TKAs (409 knees). Patellar fracture was identified in 5.2% of TKA (444 knees). Twenty-five patellae were revised (0.3%). TKA performed with a lateral release and patients with a body mass index of greater than 30 kg/m(2) were at the greatest risk of patellar loosening and fracture, respectively. Male gender, preoperative varus alignment of greater than 5 degrees , and large patellar component size also predicted a higher risk of patellar fracture. Medial patellar component position, tibial component thickness of greater than 12 mm, preoperative valgus alignment of 10 degrees or more, and preoperative flexion of 100 degrees or more predicted patellar loosening. An awareness of these factors that predict patellar failure after TKA may help determine the relative indications for TKA and influence surgical technique, especially when using this prosthesis. LEVEL OF EVIDENCE: Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Extended femoral osteotomy and proximally coated prosthesis for hip revision.

Extended trochanteric osteotomy facilitates femoral reconstruction in revision total hip arthroplasty. This study examined the outcome of extended trochanteric osteotomy combined with a proximally porous-coated calcar replacement prosthesis during revision total hip arthroplasty. Forty-five cases were reviewed with an osteotomy union rate of 98%. No femoral component was loose radiographically, and none were revised for loosening. These findings indicate excellent short-term clinical and radiographic results can be achieved with an extended trochanteric osteotomy and proximally porous-coated calcar replacement prosthesis.

Manipulation after total knee arthroplasty.

BACKGROUND: Following total knee arthroplasty, some patients who fail to achieve >90 degrees of flexion in the early perioperative period may be considered candidates for manipulation of the knee under anesthesia. The purpose of this study was to assess the outcomes of manipulation following total knee arthroplasty. METHODS: One hundred and thirteen knees in ninety patients underwent manipulation for postoperative flexion of < or =90 degrees at a mean of ten weeks after surgery. Flexion was measured with a goniometer prior to total knee arthroplasty, at the conclusion of the operative procedure, before manipulation, immediately after manipulation, at six months, and at one, three, and five years postoperatively. RESULTS: Eighty-one (90%) of the ninety patients achieved improvement of ultimate knee flexion following manipulation. The average flexion was 102 degrees prior to total knee arthroplasty, 111 degrees following skin closure, and 70 degrees before manipulation. The average improvement in flexion from the measurement made before manipulation to that recorded at the five-year follow-up was 35 degrees (p < 0.0001, paired t test). There was no significant difference in the mean improvement in flexion when patients who had manipulation within twelve weeks postoperatively were compared with those who had manipulation more than twelve weeks postoperatively. Patients who eventually underwent manipulation had significantly lower preoperative Knee Society pain scores (more pain) than those who had not had manipulation (p = 0.0027). CONCLUSIONS: Manipulation generally increases ultimate flexion following total knee arthroplasty. Patients with severe preoperative pain are more likely to require manipulation.

The effect of stuffing the patellofemoral compartment on the outcome of total knee arthroplasty.

BACKGROUND: The effect of so-called stuffing of the patellofemoral compartment at the time of total knee arthroplasty (that is, increasing the anterior patellar displacement, the anteroposterior femoral size, or the combined anteroposterior patellofemoral size) has not been well studied. The purpose of the present study was to evaluate the effect of stuffing the patellofemoral compartment on the outcome of primary total knee arthroplasty. METHODS: A retrospective review of 1100 primary total knee arthroplasties that had been performed in 1997 and 1998 was conducted. Eight hundred and thirty arthroplasties (75.5%) met the diagnostic and minimum two-year follow-up criteria for inclusion in this report. Radiographic measurements were made to determine preoperative and postoperative anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset. Regression analysis was performed to determine the effects of changes in these variables on the range of motion, the Knee Society Knee Score, the Knee Society Function Score, the Knee Society Pain Score, and the rate of lateral retinacular release. RESULTS: Preoperative to postoperative changes in anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset had no clinically meaningful effect on the range of motion of the knee or on any of the Knee Society scores. Increases in anterior patellar displacement were associated with a lower probability of the need for a lateral retinacular release. Increases in measured anteroposterior femoral size were associated with a higher probability of the need for lateral release. Even when combined, however, these relationships explained only 10.1% of the observed variance in the need for lateral retinacular release. Moreover, analyses indicated that patient gender, large as opposed to medium patellar size, and absolute femoral component size influenced the likelihood of lateral release more than did anterior patellar displacement and measured anteroposterior femoral size. CONCLUSIONS: Our findings do not support the widely held belief that stuffing of the patellofemoral joint results in adverse outcomes after total knee arthroplasty. Furthermore, the need for lateral release appears to be multifactorial and likely involves a more complex set of factors. Thus, without evidence of other identifiable causes of failure, we do not recommend revision for the treatment of pain of an overstuffed knee joint.

The effect of femoral notching during total knee arthroplasty on the prevalence of postoperative femoral fractures and on clinical outcome.

BACKGROUND: The treatment of a supracondylar femoral fracture following total knee arthroplasty is complicated by the presence of the prosthetic components. Anterior femoral notching during arthroplasty has been implicated as a contributing risk factor for femoral fracture. We retrospectively reviewed the effect of anterior femoral notching on the subsequent occurrence of a periprosthetic supracondylar fracture of the distal aspect of the femur and the outcomes of primary total knee arthroplasty in such patients. METHODS: The prevalence and depth of femoral notching were determined on a review of the lateral radiographs by observers blinded to the clinical results of 1089 consecutive total knee replacements performed in 1997 and 1998. Linear and logistic regression modeling was used to analyze the relationship between femoral notching and the prevalence of supracondylar femoral fracture, postoperative range of motion, the Knee Society score, and the Knee Society functional and pain scores. RESULTS: Femoral notching was performed in 325 (29.8%) of the 1089 knees in our series. During an average follow-up period of 5.1 years, only two supracondylar femoral fractures occurred, both in femora treated without notching. Femoral notching was not associated with an increased rate of fracture (p = 1.000) or with significant differences in the measures of outcome (range of motion [p = 0.117], knee score [p = 0.967], functional score [p = 0.861], need for a lateral release [p = 0.234], or postoperative pain [p = 0.948]). CONCLUSIONS: This study demonstrated no difference in knees managed with or without notching of the anterior distal aspect of the femur with respect to the occurrence of a supracondylar fracture, range of motion, Knee Society score, Knee Society function, or pain.

Blood management in total joint arthroplasty.

One of the primary goals in the perioperative care of orthopaedic patients undergoing surgery is the avoidance of allogeneic transfusion. There are a number of ways to lessen blood loss during surgical intervention including regional hypotensive anesthesia, careful and atraumatic surgical technique, and coagulation of bleeding surfaces. Achieving coagulation is difficult in spinal and arthroplasty procedures because of the large cancellous surfaces that are vascular and are not amenable to ligature or thermal coagulation. All measures of autologous blood salvage should be used including preoperative deposit of autologous blood, hemodilution techniques, intraoperative salvage (when appropriate), and postoperative retrieval and reinfusion. The use of perioperative recombinant erythropoietin is also a useful adjunct to promote stimulation of the bone marrow and increased red cell production. Although many infectious diseases that are transmitted through allogeneic blood transfusions have been lessened by better screening techniques, there is still potential life threatening reactions and viral transmissions that may be avoided by comprehensive blood management in joint arthroplasty.

The AGC all-polyethylene tibial component: a ten-year clinical evaluation.

BACKGROUND: While high success rates have been achieved in association with other all-polyethylene tibial components, an alarming number of failures have occurred at our institution in association with the use of an all-polyethylene version of the AGC tibial component. The purpose of the present study was to describe the survival of the AGC all-polyethylene tibial component. METHODS: Five hundred and thirty-six AGC all-polyethylene tibial components were implanted in 405 patients and were followed over a ten-year period. The average age of the patients at the time of surgery was 70.3 years, the average weight was 78 kg, and the most common diagnosis was osteoarthritis (prevalence, 92.9%). A clinical and radiographic analysis was performed, Knee Society knee and function scores were determined, and Kaplan-Meier survivorship analysis was conducted. Failure was defined as aseptic loosening as evidenced by progressive radiolucent lines and/or revision due to aseptic loosening or collapse. RESULTS: A high rate of failure was noted in the early postoperative period, with a survival rate of 90.04% (95% confidence interval, 87.35% to 92.72%) after three years. At ten years, the survival rate was 68.11% (95% confidence interval, 57.57% to 78.65%). Fifty-eight (73.4%) of seventy-nine failures occurred in association with loosening or collapse of the bone beneath the medial tibial plateau. CONCLUSION: While some all-polyethylene tibial designs have been successful, the low success rate among knees treated with the AGC all-polyethylene tibial component suggests that the results associated with all-polyethylene tibial components are design-sensitive. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Minimum ten-year follow-up of a straight-stemmed, plasma-sprayed, titanium-alloy, uncemented femoral component in primary total hip arthroplasty.

BACKGROUND: The long-term results of total hip arthroplasty without cement have been reported only rarely. The purpose of the present study was to evaluate the minimum ten-year results of primary total hip arthroplasty performed with use of a proximally porous-coated, plasma-sprayed, straight-stemmed, titanium-alloy femoral component. METHODS: The clinical and radiographic results of a consecutive series of 105 total hip replacements in ninety-five patients were reviewed ten to twelve years postoperatively. The diagnosis was osteoarthritis for seventy-seven hips (73%). The clinical result was evaluated on the basis of the Harris hip score, complications, and thigh pain. A detailed radiographic analysis was performed at each follow-up visit. Kaplan-Meier analysis was performed to evaluate the survival of the femoral component. RESULTS: The average Harris hip score improved from 46 points preoperatively to 92 points postoperatively. The average pain score at the time of the most recent follow-up was 42 points, with eighty-three hips (79%) rated as pain-free. Thigh pain was identified in only two patients. All radiolucent lines were seen around the tip of the stem. All hips had some degree of femoral remodeling consistent with osseous ingrowth. No femoral component was revised, and no femoral component had evidence of loosening. Eight acetabular components were revised because of loosening and wear, and one was revised because of recurrent dislocation. One focal femoral osteolytic lesion was seen. CONCLUSIONS: This femoral component afforded durable fixation at ten to twelve years after primary total hip arthroplasty. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Perioperative blood management practices in elective orthopaedic surgery.

Concern about the cost and safety of allogenic blood transfusion, including the risk of viral infection and immunosuppression, has led to refinements in and new approaches to blood conservation, including the development of transfusion practice standards and improvements in surgical practice. Preoperative autologous blood collection, the use of hemostatic agents, perioperative blood salvage, and the use of recombinant human erythropoietin (epoetin alfa) to stimulate erythropoiesis have contributed to decreased use of allogenic blood services. Development of appropriate blood management strategies to help reduce or eliminate exposure to allogenic blood requires a preoperative assessment of the likelihood of transfusion and of the risks as well as costs associated with conservation and replacement options. The informed selection of alternatives based on preoperative assessment of hematologic status, estimated blood loss, and sources for blood replacement may enhance blood management practices in major elective orthopaedic surgery.

The Surgeon's Role in Relative Success of PCL-Retaining and PCL-Substituting Total Knee Arthroplasty.

BACKGROUND: The orthopedic literature has not shown a universal and replicated difference, outside of flexion, in clinical results between posterior cruciate ligament retention and posterior cruciate ligament substitution in total knee arthroplasty. QUESTIONS/PURPOSES: This study was performed to compare the restoration of flexion and knee function in a large series of cruciate-retaining and cruciate-substituting total knee arthroplasties (TKRs). In addition, we aimed to study how other variables, such as those unique to each surgeon, may have affected the results. PATIENTS AND METHODS: The current study evaluated 8,607 total knee arthroplasties in 5,594 patients performed by six surgeons, each using one of four prosthesis designs (two posterior cruciate ligament retaining, two posterior cruciate ligament substituting). Knees were compared at the level of cruciate-retaining and cruciate-substituting knees, at the level of the four prostheses, and at the level of surgeon-implant combinations. Least squared means scores were obtained through multiple linear regression, analysis of variance, and the maximum likelihood method. RESULTS: At the level of posterior cruciate ligament treatment, posterior cruciate ligament substitution as a whole showed 3.2° greater flexion than posterior cruciate ligament retention. At the prosthesis level, cruciate-substituting models provided greater flexion and cruciate-retaining models provided higher function scores. In the surgeon-implant combinations, surgeons provided mixed results that often did not reflect findings from other levels; one surgeon's use of a posterior cruciate ligament retaining prosthesis achieved 14.7° greater flexion than the surgeon's use of a corresponding posterior cruciate ligament substituting design. CONCLUSIONS: Posterior cruciate ligament treatment is confounded by other variables, including the operating surgeon. The arthroplasty surgeon should choose a prosthesis based, not only on outside results, but also on personal experience and comfort.