W. Norman Scott

Development of a New Knee Society Scoring System

BackgroundThe Knee Society Clinical Rating System was developed in 1989 and has been widely adopted. However, with the increased demand for TKA, there is a need for a new, validated scoring system to better characterize the expectations, satisfaction, and physical activities of the younger, more diverse population of TKA patients.Questions/purposesWe developed and validated a new Knee Society Scoring System.MethodsWe developed the new knee scoring system in two stages. Initially, a comprehensive survey of activities was developed and administered to 101 unilateral TKA patients (53 women, 48 men). A prototype knee scoring instrument was developed from the responses to the survey and administered to 497 patients (204 men, 293 women; 243 postoperatively, 254 preoperatively) at 15 medical institutions within the United States and Canada. Objective and subjective data were analyzed using standard statistical and psychometric procedures and compared to the Knee Injury and Osteoarthritis Score and SF-12 scores for validation. Based on this analysis, minor modifications led to the new Knee Society Scoring System.ResultsWe found the new Knee Society Scoring System to be broadly applicable and to accurately characterize patient outcomes after TKA. Statistical analysis confirmed the internal consistency, construct and convergent validity, and reliability of the separate subscale measures.ConclusionsThe new Knee Society Scoring System is a validated instrument based on surgeon- and patient-generated data, adapted to the diverse lifestyles and activities of contemporary patients with TKA. This assessment tool allows surgeons to appreciate differences in the priorities of individual patients and the interplay among function, expectation, symptoms, and satisfaction after TKA.

Patellofemoral Pain After Total Knee Arthroplasty

&NA; The incidence of patellofemoral complications after total knee arthroplasty has been reported to range from 2% to 7%. Such complications include pain, subluxation, dislocation, loosening, and wear. Usually these complications are attributable to prosthetic design or surgical technique. Today, it is understood that patellofemoral prostheses must have a degree of congruence; must allow smooth, not abrupt, motion; and must restore a relatively normal size relationship between the patella and the femur. Surgical technique requires strict attention to (1) restoration of the patellofemoral spacing while avoiding “overstuffing” of the patellofemoral compartment; (2) accurate superior and medial positioning of the patellar component; (3) restoration of the rotational alignment of the femoral and tibial components; and (4) appropriate balancing of the patellofemoral soft tissues.

Histologic comparison of posterior cruciate ligaments from arthritic and age-matched knee specimens

Twenty-four posterior cruciate ligaments (PCLs) harvested at the time of total knee arthroplasty (TKA) were histologically compared with an age-matched group of 36 PCLs harvested from above-knee amputations, cadavers, and bone bank donors. Ligaments were considered histologically abnormal and degenerative if either loose, mucoid, myxoid, or cystic changes were noted. The magnitude of degeneration was defined as normal, slight, mild, moderate, or marked, based on the amount of tissue demonstrating change. Examination of the PCLs from the TKA group demonstrated 17% normal ligaments, 20% with mild focal changes, and 63% with marked degenerative changes. The control group demonstrated 45% normal cruciate ligaments and 33% with slight, 11% with mild, and 11% with moderate focal changes. No PCL from the control group showed marked changes. The overall degenerative changes between these two groups were found to be statistically significant (P < .001). This study demonstrated that the PCL obtained at the time of TKA is characterized by distinct histologic degenerative changes that are different from age-related changes (P < .001) and that the PCL is not spared degenerative changes in involved osteoarthritic knees. This may help explain the finding that the PCL in osteoarthritic knees is biomechanically abnormal. Many studies have reported excellent results with TKA systems that retain the PCL, implying that a completely normal PCL is not required or that neural input is sufficient for proper kinematic knee function in knees that have undergone total joint arthroplasty.

Mobile Bearings in Primary Knee Arthroplasty

&NA; Mobile‐bearing knee arthroplasty (MBKA) has potential advantages compared with conventional fixed‐bearing total knee arthroplasty (TKA). By allowing unconstrained axial rotation, MBKA can offer greater articular conformity without an increased probability of loosening due to increased axial torque. Increased articular conformity minimizes polyethylene contact stresses, thereby reducing linear wear and subsurface fatigue failure. Axial rotation of the platform also enables self‐correction of tibial component malrotation. Despite these advantages, the long‐term clinical results obtained with current MBKA devices are similar to those obtained with well‐designed fixed‐bearing TKA prostheses, with no data suggesting their superiority. The disadvantages of MBKA include bearing dislocation and breakage, soft‐tissue impingement, a steep technique learning curve, and concerns about volumetric wear. Hypothetically, longer‐term followup of MBKA results may reveal a significant difference from fixed‐bearing TKA results as the fatigue failure threshold of incongruent polyethylene is exceeded.

Long-term results of total knee arthroplasty after the use of soft tissue expanders

The success of total knee arthroplasty can be jeopardized by poor wound healing. In the current study, the results of knee arthroplasty after soft tissue expansion were reviewed retrospectively in 27 patients (29 knees) at risk for problematic healing. The incidence of wound complications was recorded for all patients after the expansion procedure and the arthroplasty. A Knee Society score also was calculated at the latest evaluation. Minor wound complications occurred after 21% (six of 29) of the tissue expansion procedures and after 18% (five of 28) of the subsequent arthroplasties. One major wound complication occurred during tissue expansion necessitating abandonment of the planned arthroplasty. No major wound complications occurred in those patients who underwent knee arthroplasty. At an average followup of 34.4 months, the average Knee Society score was 83.7 points. The results of the current study show that the technique of soft tissue expansion before total knee arthroplasty in patients at high risk for wound healing problems can successfully prevent catastrophic wound complications after the arthroplasty procedure and can avoid the need for disfiguring soft tissue reconstructions.

Primary Total Knee Arthroplasty

• Understand correction of fixed deformity in primary total knee arthroplasty via the harmonization of osseous resection and soft-tissue balance • Understand the pitfalls in the surgical technique of balancing a total knee prosthesis.

SOFT TISSUE EXPANSION PRIOR TO ARTHROPLASTY IN THE MULTIPLY-OPERATED KNEE : A NEW METHOD OF PREVENTING CATASTROPHIC SKIN PROBLEMS

Ten knees in nine patients underwent gradual soft tissue expansion prior to major knee surgery. All patients had multiple prior operative procedures around the knee. The resultant multiple skin incisions were felt to potentially jeopardize the postoperative status of the soft tissues. Each knee underwent the surgical placement of a tissue expander through a bed of adjacent healthy soft tissue followed by the gradual inflation of the expander over an average of 64.5 days. The average volume of soft tissue expansion was 313.7 mL per knee. Subsequent major knee surgery requiring an arthrotomy was performed at the time of expander removal followed by uncomplicated soft tissue closure. All wounds healed without any complications.

The practice of unicompartmental knee arthroplasty in the United Kingdom

Purpose. To survey the current practice of unicompartmental knee arthroplasty (UKA) in the United Kingdom. Methods. Questionnaires were sent to all 341 local members of the British Association for Surgery of the Knee to inquire into their practice of UKA, including clinical indications, preoperative investigations, surgical approach, preferences in implant design, and the role of UKA in relation to high tibial osteotomy. Result. 56% of respondents performed less than 16 UKAs per year, whereas 16.5% performed over 30 per year. 89.5% of the respondents used anteroposterior radiographs as their main investigation tool. Only 30% and 16.5% used posteroanterior 30° flexion and varus/valgus stress radiographs, respectively, despite being better investigation tools. 57% considered arthroscopy, despite its invasive nature. The main contra-indications to UKA were anterior cruciate ligament deficiency with instability (95%), focal grade-III osteoarthritis in the contralateral compartment (87%), and osteoporosis with rheumatoid arthritis (80.5%), but only 59% of respondents considered an inability to passively correct a pre-existing varus or valgus deformity as a contra-indication. 51.5% of respondents preferred minimally invasive approach, 96% preferred cemented fixation, and over two thirds used the mobile bearing design. 72% of respondents expressed preference for total knee arthroplasty over UKA in localised lateral compartment osteoarthritis. Conclusion. Modern UKA has gained popularity in properly selected patients with localised medial compartment osteoarthritis, provided the knee is not anterior cruciate ligament deficient and any deformity is passively correctable.

Evaluation of patella viability after disruption of the arterial circulation

Fifty patients whose surgical approach violated the arterial geniculate circulation to the patella were evalu ated to determine the subsequent effect on patella viability. Comparative postoperative radionuclide scans in 100 knees, 50 control and 50 surgical, revealed an avascular insult in only 7 knees (14%). It appears that the intratendinous circulation described by Björkström and Goldie1 protects the patella from an avascular insult in the presence of geniculate arterial disruption.

Blood management in revision total knee arthroplasty.

Much attention has been focused on blood management issues in orthopaedic surgery in recent years, but blood management in patients having revision total knee arthroplasty is not well-established. Hematologic values and transfusion records of 100 patients (52 women, 48 men; mean age, 65 years) who had aseptic revision total knee arthroplasty at the authors’ institution were evaluated retrospectively. Two- or three-component revisions comprised 66% of the procedures, and 58 patients participated in a preoperative autologous donation program. The mean preoperative hemoglobin level was 12.1 g/dL in the women and 14.1 g/dL in the men, but the men experienced a greater decrease in hemoglobin level (mean largest decrease, 4.2 g/dL versus 3.1 g/dL), possibly caused by the higher allogeneic transfusion rate in women (19.2%) versus men (4.2%). Patient age did not influence hemoglobin level or transfusion rates. Patients who participated in a preoperative autologous donation program had significantly higher hemoglobin levels before donation (14.4 g/dL versus 13.3 g/dL for patients who did not participate in a program) but comparable hemoglobin levels after predonation (12.9 g/dL). Patients with preoperative hemoglobin levels less than 13 g/dL were significantly more likely to have a transfusion. Symptom-based transfusion strategies and blood management approaches such as epoetin alfa that elevate preoperative hemoglobin level therefore may be beneficial in patients having revision total knee arthroplasty.