Men and Women Demonstrate Differences in Early Functional Recovery After Total Knee Arthroplasty.

OBJECTIVE: To investigate whether sex affects the trajectory of functional recovery after total knee arthroplasty (TKA). DESIGN: Retrospective analysis from a historical database containing data from 3 prospective clinical trials and a pilot study. SETTING: Clinical laboratory setting. PARTICIPANTS: Recruitment across studies was restricted to patients who underwent an elective unilateral TKA for the treatment of osteoarthritis and were between 50 and 85 years of age (N=301). INTERVENTIONS: Across all 4 studies, patients received a TKA and physical therapy intervention. Measures of physical function and strength were assessed before TKA and 1, 3, and 6 months after TKA. MAIN OUTCOME MEASURES: Using a repeated-measures maximum likelihood model, statistical inference was made to estimate the changes in outcomes from before surgery to 1, 3, and 6 months after TKA that were stratified by sex. Muscle strength was assessed during maximal isometric quadriceps and hamstrings contractions. Muscle activation was assessed in the quadriceps muscle. Physical function outcomes included timed Up and Go (TUG) test, stair climbing test, and 6-minute walk test (6MWT). RESULTS: Women demonstrated less decline in quadriceps strength than did men at 1, 3, and 6 months after TKA (P<.04), whereas women demonstrated less decline in hamstrings strength 1 month after TKA (P<.0001). Women demonstrated a greater decline than did men on the TUG test (P=.001), stair climbing test (P=.004), and 6MWT (P=.001) 1 month after TKA. Sex differences in physical function did not persist at 3 and 6 months after TKA. CONCLUSIONS: Sex affected early recovery of muscle and physical function in the first month after TKA. Women demonstrated better preservation of quadriceps strength but a greater decline on measures of physical function than did men.

Bilateral Symmetrical Comparison of Femoral and Tibial Anatomic Features.

BACKGROUND: Variability in morphologic features of the human lower extremity within and across populations has been reported, but limb asymmetry within individuals is often overlooked. For example, in 19 studies of version of the lower extremity in the literature, 6 document asymmetry in the population, but none of these reports document asymmetry in an individual. The aim of this study was to identify the (a)symmetry and quantify variability in the tibiae and femora of matched pairs of limbs. More specifically, using a computed tomography scan database tool, we (1) identified (a)symmetry between paired left and right legs for angulation, version, and alignment features and (2) calculated the percentage of paired limbs with >1° of (a)symmetry for each evaluated parameter. METHODS: Computerized axial tomographic scans (<1.0 mm slices) from bilateral lower limbs of 361 skeletally mature subjects without bone pathology were prospectively acquired. Bones were segmented and morphologic features were measured. RESULTS: Angular features are symmetric left to right, but rotational features are not, with 7° of mean asymmetry in femoral anteversion (range: 0°-23°) and 3° of asymmetry in tibial version (range: 0°-8°). CONCLUSIONS: This study disproves the hypothesis that human limbs are absolutely symmetric, confirming instead that there is asymmetry in version between left and right paired limbs. Surgeons strive for symmetry in lower extremity reconstruction, and they often compare side to side in outcome studies, believing that normal limbs are absolutely symmetric when this is not necessarily true. These assumptions concerning lower extremity symmetry need to be reassessed.

Successful LCL reconstruction and PCL repair for LCL tear and PCL avulsion following total knee arthroplasty.

Total knee arthroplasty represents a well-established and successful procedure; however, ligament incompetence is known to negatively affect surgical outcomes. Here we present an unusual case of early total knee arthroplasty failure secondary to femoral posterior cruciate ligament (PCL) avulsion and associated lateral collateral ligament (LCL) tear, treated successfully with primary PCL repair and LCL reconstruction. For LCL reconstruction, a peroneus longus allograft was passed through an anterior to posterior bony tunnel in the fibular head and docked into a horizontal femoral tunnel. Level of evidence Case report, Level IV.

Cylindrical axis, not epicondyles, approximates perpendicular to knee axes.

BACKGROUND: The transepicondylar axis (TEA) is often used as a surrogate for the flexion-extension axis, ie, the axis around which the tibia moves in space, because of a belief that both axes lie perpendicular to the mechanical axis. However, studies suggest the cylindrical axis (CA), defined as a line equidistant from contact points on the medial and lateral condylar surfaces from 10(o) to 120(o) flexion, more closely approximates the axis around which the tibia moves in space. QUESTIONS/PURPOSES: We examined the TEA and CA angles relative to mechanical axes to determine whether one more consistently and closely approximates the surgical goal of orthogonality to the mechanical axis. METHODS: Three-dimensional (3-D) models were reconstructed from CT scans of five cadaver limbs. Three observers repeated three measurement sets to locate the TEA, CA, and femoral mechanical and tibial mechanical axes. Angles of the TEA and CA relative to the mechanical axes were calculated in two-dimensions (2-D) and as 3-D projections and compared for differences in magnitude and variance. RESULTS: Angles between CA and the mechanical axes were closer to 90° than the TEA in 2-D (92° versus 94° for the femur, 93° versus 94° for the tibia) and 3-D (88° versus 87° for the femur, 88° versus 86° for the tibia). Variance of the TEA was higher than the CA in 2-D. CONCLUSIONS: The CA forms angles more orthogonal to the mechanical axes of the thigh and leg than the TEA. CLINICAL RELEVANCE: Although we found a consistently greater deviation of the TEA from the mechanical axis than the CA with small differences, future studies will need to determine whether these differences are biomechanically or clinically important.

Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty.

BACKGROUND/RATIONALE: Although TKA reliably reduces pain from knee osteoarthritis, full recovery of muscle strength and physical function to normal levels is rare. We presumed that a better understanding of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function. QUESTIONS/PURPOSES: The purposes of this study were to (1) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison, and (2) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs. METHODS: We prospectively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1, 3, and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults. Bilateral, isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction. RESULTS: There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup, although differences existed when compared with nonoperative and healthy control legs. Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month (144.5%) compared to the nonoperative leg. CONCLUSIONS: Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocols, hamstrings dysfunction also is present and should be addressed. CLINICAL RELEVANCE: Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes.

Quadriceps/hamstrings co-activation increases early after total knee arthroplasty.

UNLABELLED: Quadriceps and hamstrings weakness and co-activation are present following total knee arthroplasty (TKA) and may impair functional performance. How surgery and post-operative rehabilitation influence muscle activation during walking early after surgery is unclear. PURPOSE: Examine muscle strength and activation during walking before and one and 6-months post-TKA. METHODS: Ten patients (n=6 female; age: 64.7 ± 7.9 years; body mass index[BMI]:29.2 ± 2.5 kg/m(2)) and 10 healthy adults (n=6 female; age: 60.6 ± 7.4 years; BMI: 25.5 ± 4.0 kg/m(2)) participated. The patients underwent bilateral quadriceps and hamstrings strength testing and assessment of quadriceps/hamstrings co-activation and on/off timing using surface electromyography during a six-minute walk test (6MW). Groups, limbs, and changes with TKA surgery were compared. RESULTS: Patients reported greater 6MW knee pain pre- versus post-TKA and compared to controls (P<0.05). Patients had weaker surgical limb hamstrings (P<0.05) and bilateral quadriceps (P<0.05) strength than controls pre- and post-TKA. Before and 1-month post-TKA, patients had side-to-side differences in quadriceps and hamstrings strength (P<0.05). Controls walked farther than patients (P<0.01). Patients demonstrated greater surgical limb co-activation pre-operatively than controls (P<0.05). Co-activation was higher bilaterally one-month post-TKA compared to controls (P<0.05). Patients turned off their quadriceps later during stance than controls before and 1-month post-TKA (P<0.05). CONCLUSIONS: Muscle strength, co-activation, and timing differed between patients and controls before and early after surgery. Rehabilitation to improve strength and muscle activation seems imperative to restore proper muscle firing patterns early after surgery.

Improving residency training in arthroscopic knee surgery with use of a virtual-reality simulator. A randomized blinded study.

BACKGROUND: There is a paucity of articles in the surgical literature demonstrating transfer validity (transfer of training). The purpose of this study was to assess whether skills learned on the ArthroSim virtual-reality arthroscopic knee simulator transferred to greater skill levels in the operating room. METHODS: Postgraduate year-3 orthopaedic residents were randomized into simulator-trained and control groups at seven academic institutions. The experimental group trained on the simulator, performing a knee diagnostic arthroscopy procedure to a predetermined proficiency level based on the average proficiency of five community-based orthopaedic surgeons performing the same procedure on the simulator. The residents in the control group continued their institution-specific orthopaedic education and training. Both groups then performed a diagnostic knee arthroscopy procedure on a live patient. Video recordings of the arthroscopic surgery were analyzed by five pairs of expert arthroscopic surgeons blinded to the identity of the residents. A proprietary global rating scale and a procedural checklist, which included visualization and probing scales, were used for rating. RESULTS: Forty-eight (89%) of the fifty-four postgraduate year-3 residents from seven academic institutions completed the study. The simulator-trained group averaged eleven hours of training on the simulator to reach proficiency. The simulator-trained group performed significantly better when rated according to our procedural checklist (p = 0.031), including probing skills (p = 0.016) but not visualization skills (p = 0.34), compared with the control group. The procedural checklist weighted probing skills double the weight of visualization skills. The global rating scale failed to reach significance (p = 0.061) because of one extreme outlier. The duration of the procedure was not significant. This lack of a significant difference seemed to be related to the fact that residents in the control group were less thorough, which shortened their time to completion of the arthroscopic procedure. CONCLUSIONS: We have demonstrated transfer validity (transfer of training) that residents trained to proficiency on a high-fidelity realistic virtual-reality arthroscopic knee simulator showed a greater skill level in the operating room compared with the control group. CLINICAL RELEVANCE: We believe that the results of our study will stimulate residency program directors to incorporate surgical simulation into the core curriculum of their residency programs.

Muscle activation and coactivation during five-time-sit-to-stand movement in patients undergoing total knee arthroplasty.

Quadriceps weakness is prevalent with knee osteoarthritis (OA) and after total knee arthroplasty (TKA). To compensate for quadriceps dysfunction, patients often alter movement strategies. Little is known about muscle coordination during sit-to-stand (concentric) and stand-to-sit (eccentric) movements in the acute postoperative period. This investigation characterized the distribution of muscle activation between the concentric and eccentric phases during a five-time-sit-to-stand (FTSTS) movement in late stage OA and one month after TKA. Patients and healthy participants performed a FTSTS while recording bilateral ground reaction forces (GRFs) and electromyography (EMG). Concentric and eccentric ensemble averages of the GRF and EMG were calculated for the concentric and eccentric phases. Coactivation indices, integrated EMG, and GRF were calculated for each limb and phase. Patients demonstrated higher eccentric coactivation than the healthy group. Postoperative loading was higher in the nonsurgical limb. Postoperative quadriceps activity was lower in the concentric phase and higher in the eccentric phase than the healthy group. Higher coactivation in the patients resulted from sustained distribution of quadriceps activity throughout the eccentric phase. This indicated an inability to coordinate muscle firing when rapidly lowering to a chair and occurred despite unloading of the surgical limb. Although these patterns may serve as a protective strategy, they may also impede recovery of muscle function after TKA.

Muscle strength loss in the lower limb after total knee arthroplasty.

OBJECTIVE: This study aimed to examine functional mobility and strength loss in the ankle plantarflexors and dorsiflexors and knee extensors and flexors after total knee arthroplasty. DESIGN: This was a prospective, longitudinal cohort study. Maximal voluntary isometric contractions and gait speed assessments were performed before and after total knee arthroplasty. RESULTS: Twenty patients undergoing primary total knee arthroplasty were followed. Repeated-measures analysis of variance results indicated an effect of time on muscle strength, with all muscle groups being significantly weaker (knee extensors, P < 0.001; knee flexors, P < 0.001, ankle plantarflexors, P = 0.004; ankle dorsiflexors, P < 0.001) 1 mo postoperatively. Knee extensors were 42% weaker than preoperative levels, and knee flexors were 34% weaker, whereas the ankle plantarflexors were 17% weaker, and the dorsiflexors were 18% weaker. Three and 6 mos after surgery, strength in all muscle groups was similar to preoperative levels (P > 0.05 for all muscle groups). Patient function followed a similar trend, with patients walking slower 1 mo postoperatively (P < 0.001) and recovering to preoperative levels by 3 and 6 mos after surgery (P > 0.05). CONCLUSIONS: Patients may benefit from early postoperative rehabilitation, including strengthening of the plantarflexors and dorsiflexors, although strengthening of the quadriceps and hamstrings muscles should continue to be a priority.

Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial.

BACKGROUND: The recovery of quadriceps muscle force and function after total knee arthroplasty (TKA) is suboptimal, which predisposes patients to disability with increasing age. OBJECTIVE: The purpose of this investigation was to evaluate the efficacy of quadriceps muscle neuromuscular electrical stimulation (NMES), initiated 48 hours after TKA, as an adjunct to standard rehabilitation. DESIGN: This was a prospective, longitudinal randomized controlled trial. METHODS: Sixty-six patients, aged 50 to 85 years and planning a primary unilateral TKA, were randomly assigned to receive either standard rehabilitation (control) or standard rehabilitation plus NMES applied to the quadriceps muscle (initiated 48 hours after surgery). The NMES was applied twice per day at the maximum tolerable intensity for 15 contractions. Data for muscle strength, functional performance, and self-report measures were obtained before surgery and 3.5, 6.5, 13, 26, and 52 weeks after TKA. RESULTS: At 3.5 weeks after TKA, significant improvements with NMES were found for quadriceps and hamstring muscle strength, functional performance, and knee extension active range of motion. At 52 weeks, the differences between groups were attenuated, but improvements with NMES were still significant for quadriceps and hamstring muscle strength, functional performance, and some self-report measures. LIMITATIONS: Treatment volume was not matched for both study arms; NMES was added to the standard of care treatment. Furthermore, testers were not blinded during testing, but used standardized scripts to avoid bias. Finally, some patients reached the maximum stimulator output during at least one treatment session and may have tolerated more stimulation. CONCLUSIONS: The early addition of NMES effectively attenuated loss of quadriceps muscle strength and improved functional performance following TKA. The effects were most pronounced and clinically meaningful within the first month after surgery, but persisted through 1 year after surgery.

Relationship between intensity of quadriceps muscle neuromuscular electrical stimulation and strength recovery after total knee arthroplasty.

BACKGROUND: Neuromuscular electrical stimulation (NMES) can facilitate the recovery of quadriceps muscle strength after total knee arthroplasty (TKA), yet the optimal intensity (dosage) of NMES and its effect on strength after TKA have yet to be determined. OBJECTIVE: The primary objective of this study was to determine whether the intensity of NMES application was related to the recovery of quadriceps muscle strength early after TKA. A secondary objective was to quantify quadriceps muscle fatigue and activation immediately after NMES to guide decisions about the timing of NMES during rehabilitation sessions. DESIGN: This study was an observational experimental investigation. METHODS: Data were collected from 30 people who were 50 to 85 years of age and who received NMES after TKA. These people participated in a randomized controlled trial in which they received either standard rehabilitation or standard rehabilitation plus NMES to the quadriceps muscle to mitigate strength loss. For the NMES intervention group, NMES was applied 2 times per day at the maximal tolerable intensity for 15 contractions beginning 48 hours after surgery over the first 6 weeks after TKA. Neuromuscular electrical stimulation training intensity and quadriceps muscle strength and activation were assessed before surgery and 3.5 and 6.5 weeks after TKA. RESULTS: At 3.5 weeks, there was a significant association between NMES training intensity and a change in quadriceps muscle strength (R(2)=.68) and activation (R(2)=.22). At 6.5 weeks, NMES training intensity was related to a change in strength (R(2)=.25) but not to a change in activation (R(2)=.00). Furthermore, quadriceps muscle fatigue occurred during NMES sessions at 3.5 and 6.5 weeks, whereas quadriceps muscle activation did not change. LIMITATIONS: Some participants reached the maximal stimulator output during at least 1 treatment session and might have tolerated more stimulation. CONCLUSIONS: Higher NMES training intensities were associated with greater quadriceps muscle strength and activation after TKA.

Report of a group developing a virtual reality simulator for arthroscopic surgery of the knee joint.

Apprenticeship training of surgical skills is time consuming and can lead to surgical errors. Our group is developing an arthroscopic virtual reality knee simulator for training orthopaedic residents in arthroscopic surgery before live-patient operating room experience. The simulator displays realistic human knee anatomy derived from the Visible Human Dataset developed by the National Library of Medicine and incorporates active force-feedback haptic technology. Our premise is that postgraduate year 2 residents completing a formal virtual education program who are trained to reach a proficiency standard in the techniques and protocol for an arthroscopic knee examination will complete a diagnostic arthroscopy on an actual patient in less time with greater accuracy, less iteration of movement of the arthroscope, and less damage to the patient's tissue compared with residents in the control group learning and practicing the arthroscopic knee examination procedures through the residency program's established education and training program. The validation study, done at eight orthopaedic residency programs, will commence in early 2006 and will take one year to complete. We anticipate that proficiency obtained on the simulator will transfer to surgical skills in the operating room.

Variability of landmark identification in total knee arthroplasty.

Virtual reality is new technology that is finding application in many facets of orthopaedics. We will describe an application of virtual reality in orthopaedic research. Component placement in total knee arthroplasty depends on identification of anatomic landmarks about the knee. We surmised significant interobserver variability occurs in the identification of landmarks of the distal femur used in total knee arthroplasty. The results tested in virtual space show that certain anatomic landmarks used in total knee arthroplasty are not reliable. The significance of this observation is that landmark identification, an integral component of computer-assisted surgical navigation in total knee arthroplasty, represents a source of method error in an otherwise accurate and precise computer-assisted technique.