Long-term outcome of total knee arthroplasty in patients with morbid obesity.

INTRODUCTION: Patients with morbid obesity and advanced painful knee osteoarthritis are considered as poor candidates for total knee replacement. Our aims were to evaluate the outcomes of TKR surgery and the risks for post-operative complications in patients with morbid obesity (BMI > 40 kg/m2) as compared with obese patients (30 < BMI ≤ 40 kg/m2) and non-obese patients, BMI < 30 kg/m2); to evaluate if there are differences between morbid-obese patients (BMI 40-49.99 kg/m2) and extreme morbid obese patients (BMI > 50 kg/m2); and to present some surgical tips which can improve the TKR outcomes in morbid obese patients. MATERIALS AND METHODS: There were successive 333 patients, of them 39 patients (11.7%) were lost for follow-up. So, this series included 292 patients - 82 with bilateral TKR- and 374 TKR. The mean age was 64.3 years old (48-83 years) and the mean follow-up 10.8 years (4-17 years). The KSS and FKSS scores were calculated at the end of the follow-up period and compared to the pre-operative evaluation. Radiographic assessment at the end of follow-up included evaluation of implant position, alignment, and presence of radiolucent lines around the implants and was compared with the immediate post-operative radiographs. Statistical analysis was performed using SPSS v 22.0. RESULTS: Our findings showed marked improvement following TKR of non-obese, obese, and morbid obese patients, regarding the KSS and FKSS. Significant change was observed between the non-obese and obese patients as compared to morbid obese patients. There were no significant differences between morbid obese patients with BMI > 40 versus those with BMI > 50. There was a slight increased risk of early complications following TKR in morbid obese patients such as skin necrosis and infection around the surgical incision. CONCLUSIONS: Marked improvement was observed in the three groups of patients after TKR, although non-obese and obese groups had better mean scores of KSS and FKSS than morbid obese patients. No significant differences were found within the morbid obese patients themselves. Therefore, we believe that morbid obese patients are appropriate candidates and can enjoy the benefits of total knee arthroplasty done with careful use of some surgical tips presented in our study.

Unicompartmental knee arthroplasty versus total knee arthroplasty: Which type of artificial joint do patients forget?

PURPOSE: During recent years, there has been an intensive growth of interest in the patient's perception of functional outcome. The Forgotten Joint Score (FJS) is a recently introduced score that measures joint awareness of patients who have undergone knee arthroplasty and is less limited by ceiling effects. The aim of this study was to compare the FJS between patients who undergo medial unicompartmental knee arthroplasty (UKA) and patients who undergo total knee arthroplasty (TKA) 1 and 2 years post-operatively. METHODS: This prospective study compares the FJS at a minimum of one (average 1.5 years, range 1.0-1.9) and a minimum of 2 years (average 2.5 years, range 2.0-3.6) post-operatively between patients who underwent medial UKA and TKA. RESULTS: One-hundred and thirty patients were included. Sixty-five patients underwent medial UKA and 65 patients underwent TKA. At both follow-up points, the FJS was significantly higher in the UKA group (FJS 1 year 73.9 ± 22.8, FJS 2 year 74.3 ± 24.8) in contrast to the TKA group (FJS 1 year 59.3 ± 29.5 (p = 0.002), FJS 2 year 59.8 ± 31.5, (p = 0.004)). No significant improvement in the FJS was observed between 1- and 2-year follow-up of the two cohorts. CONCLUSION: Patients who undergo UKA are more likely to forget their artificial joint in daily life and consequently may be more satisfied. LEVEL OF EVIDENCE: II.

Comparison of Lateral Closing-Wedge Versus Medial Opening-Wedge High Tibial Osteotomy on Knee Joint Alignment and Kinematics in the ACL-Deficient Knee.

BACKGROUND: Lateral closing-wedge (LCW) and medial opening-wedge (MOW) high tibial osteotomies (HTOs) correct varus knee alignment and stabilize the anterior cruciate ligament (ACL)-deficient knee. Tibiofemoral and patellofemoral alignment and kinematics after HTO are not well quantified. PURPOSE: To compare the effect of LCW and MOW HTO on tibiofemoral and patellofemoral alignment in the ACL-deficient knee. STUDY DESIGN: Controlled laboratory study. METHODS: Anterior drawer, Lachman, and pivot-shift tests were performed on cadaveric specimens (N = 16), and anterior tibial translation and tibial rotation were measured for the native and ACL-sectioned knee. The right and left knee of each cadaveric specimen underwent an LCW and MOW HTO, respectively, and stability testing was repeated. All cadavers underwent pre- and postosteotomy computerized tomography with 3-dimensional computer modeling to determine the effect of HTO on posterior tibial slope, as well as tibial and patellofemoral axial plane alignment (tibial axial rotation and patellar axial tilt). RESULTS: Correction to neutral coronal alignment was obtained with both osteotomy techniques; however, larger posterior tibial slope neutralization was achieved with LCW compared with MOW (mean ± SD, 11° ± 3.8° vs 5° ± 5°). LCW demonstrated a greater decrease in anterior tibial translation (P < .05) during Lachman testing, with translation values approximating those of the native knee, especially for the lateral compartment. A similar decrease in anterior tibial translation with LCW was not found during anterior drawer testing. Anterior tibial translation did not improve for either the Lachman or the anterior drawer test after MOW. Osteotomy type did not affect tibial rotation with pivot shift. Relative to MOW, LCW resulted in greater tibial axial rotation and patellar axial tilt (7.7° ± 4° and 5.6° ± 3.9° [LCW], 2.8° ± 2.3° and 2.4° ± 0.9° [MOW], respectively; P < .05). CONCLUSION/CLINICAL RELEVANCE: LCW shows more reproducible posterior tibial slope neutralization and decreased anterior tibial translation in ACL deficiency compared with MOW; however, LCW is associated with increased external tibial axial rotation and lateral patellar tilt, which may adversely affect the patellofemoral joint. More work is needed to understand the clinical and functional outcome of these biomechanical findings in the ACL-deficient knee.

The ACL Graft Has Different Cross-sectional Dimensions Compared With the Native ACL: Implications for Graft Impingement.

BACKGROUND: Impingement of anterior cruciate ligament (ACL) grafts against the femoral notch and the posterior cruciate ligament (PCL) is thought to be influenced primarily by tunnel position and graft orientation. Recent data have implied that the native ACL is ribbon-shaped. PURPOSE: To evaluate the 3-dimensional shape and cross-sectional area of the native ACL versus the ACL graft and to compare the degree of impingement against the femoral notch and PCL. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Bilateral knee magnetic resonance images were analyzed for 27 patients with unilateral bone-patellar tendon-bone (BPTB) ACL reconstruction performed via transtibial or anteromedial portal femoral tunneling techniques. Three-dimensional models of the ACL, PCL, femur, and tibia were digitally rendered. The cross-sectional area and dimensions of the native ACL and the reconstructed graft were determined at 3 equally spaced locations and compared via Wilcoxon-Mann-Whitney and Kruskal-Wallis tests. In addition, impingement of the ACL on the PCL and femoral notch was graded in 3 groups. Chi-square or Fisher exact tests were used to compare the proportional differences of impingement of the native and reconstructed ACL on the PCL and femoral notch, respectively. All analyses were performed using 2-sided hypothesis testing, with statistical significance at P < .05. RESULTS: Cross-sectional areas at all 3 points on the ACL graft were significantly greater than those of the native ACL (P < .001). The long- to short-axis ratio for the native ACL was significantly greater at each location compared with the corresponding locations along the ACL graft (P < .001), implying that the native ACL is "flatter" than is an ACL graft. There were 19 operated knees (70%) with contact or impingement between the ACL graft and the femoral notch compared with zero knees with a native ACL (P < .001). In addition, 22 operated knees (81%) showed contact or impingement between the ACL graft and the PCL, compared with 7 knees (26%) with a native ACL (P < .001). No significant differences in impingement frequency were noted between the transtibial and anteromedial tunneling techniques for ACL graft specimens (P > .05). CONCLUSION: Native ACLs have a smaller cross-sectional area, are "flatter," and experience less incidence of impingement compared with anatomically placed BPTB ACL grafts.

Medial unicompartmental knee arthroplasty improves congruence and restores joint space width of the lateral compartment.

BACKGROUND: Osteoarthritic progression of the lateral compartment remains a leading indication for medial unicompartmental knee arthroplasty (UKA) revision. Therefore, the purpose of this study was to evaluate the alterations of the lateral compartment congruence and joint space width (JSW) following medial UKA. METHODS: Retrospectively, lateral compartment congruence and JSW were evaluated in 174 knees (74 females, 85 males, mean age 65.5years; SD±10.1) preoperatively and six weeks postoperatively, and compared to 41 healthy knees (26 men, 15 women, mean age 33.7years; SD±6.4). Congruence (CI) was calculated using validated software that evaluates the geometric relationship between surfaces and calculates a congruence index (CI). JSW was measured on three sides (inner, middle, outer) by subdividing the lateral compartment into four quarters. RESULTS: The CI of the control group was 0.98 (SD±0.01). The preoperative CI was 0.88 (SD±0.01), which improved significantly to 0.93 (SD±0.03) postoperatively (p<0.001). In 82% of knees, CI improved after surgery, while in 18% it decreased. The preoperative significant JSW differences of the inner (p<0.001) and outer JSW (p<0.001) were absent postoperatively. CONCLUSION: Our data suggests that a well-conducted medial UKA not only resurfaces the medial compartment but also improves congruence and restores the JSW of the lateral compartment.

Predictors of Subjective Outcome After Medial Unicompartmental Knee Arthroplasty.

BACKGROUND: Unexplainable pain after medial unicompartmental knee arthroplasty (UKA) remains a leading cause for revision surgery. Therefore, the aim of this study is to identify the patient-specific variables that may influence subjective outcomes after medial UKA to optimize results. METHODS: Retrospectively, we analyzed 104 consecutive medial UKA patients. The evaluated parameters consisted of age, body mass index, gender, preoperative radiographic severity of the various knee compartments, and preoperative and postoperative mechanical axis alignments. RESULTS: At an average of 2.3-year follow-up, our data demonstrate that body mass index, gender, and preoperative severity among the various knee compartments do not influence Western Ontario and McMaster Universities Arthritis Index (WOMAC) results. Preoperatively, patients aged <65 years had inferior WOMAC stiffness (4.6 vs 2.9, P = .001), pain (9.7 vs 7.6, P = .041), and total (37.2 vs 47.6, P = .028) scores vs patients aged ≥65 years. Postoperatively, only the difference on the WOMAC stiffness subscale remained significant between both age groups, in favor of patients aged ≥65 years (1.0 vs 1.5, P = .035). A postoperative varus mechanical axis alignment of 1°-4° correlated to significantly superior WOMAC pain (P = .03), function (P = .04), and total (P = .04) scores compared to a varus of ≤1° or ≥4°. CONCLUSION: Our data suggest that greater pain relief can be expected in patients aged <65 years and that a postoperative lower limb alignment of 1°-4° varus should be pursued. Taking these factors into consideration will help to maximize clinical outcomes, fulfill patient expectations after medial UKA, and subsequently minimize revision rates.

Coronal tibiofemoral subluxation in knee osteoarthritis.

OBJECTIVE: To analyze knees in varying stages of osteoarthritis (OA) for the presence of coronal tibiofemoral (CTF) subluxation and to determine if CTF subluxation severity is related to knee OA worsening. METHODS: We retrospectively evaluated CTF subluxation and limb alignment in 113 patients with different stages of knee OA who were being considered for an arthroplasty procedure. Knee OA was classified as "mild" or "severe" according to Kellgren-Lawrence scale. CTF subluxation was measured in the study groups and in 40 knees of healthy controls using software developed specifically on the basis of Iterative Closest Point mathematical algorithm. RESULTS: Mean CTF subluxation in "mild OA" and "severe OA" groups was 3.5% (±2) and 3.5 % (±5) of the tibial plateau, respectively. For both the mild and severe OA groups, CTF subluxation was significantly increased compared to the 1.4% (±1) CTF subluxation in the control group, (p < 0.0001) and (p = 0.012), respectively. However, there was no significant difference in CTF subluxation between the mild OA and severe OA groups (p = 0.75). Limb varus malalignment in mild OA and severe OA groups was 3.6° (±2.2) and 5.3° (±2.6), respectively. Both significantly increased comparing to the 1° (±0.7) control group alignment (p < 0.0001). Varus malalignment in the severe OA group was significantly increased comparing to the mild OA group (p = 0.0003). CONCLUSIONS: CTF subluxation is a radiographic finding related to knee OA which occurs mainly in the early stages of the osteoarthritic process and stagnates as OA progresses.

Medial Subluxation of the Tibia After Anterior Cruciate Ligament Rupture as Revealed by Standing Radiographs and Comparison With a Cadaveric Model.

BACKGROUND: Biomechanical studies indicate that the tibia shifts medially and has a more valgus orientation in the anterior cruciate ligament (ACL)-deficient knee. However, it is not known whether these differences can be detected on standing radiographs. PURPOSE: To determine whether medial subluxation and more changes in coronal alignment of the tibia are detectable in both weightbearing radiographs and a cadaveric model simulating quiet standing. STUDY DESIGN: Case series; Level of evidence, 4, and Descriptive laboratory study. METHODS: Radiographic data were available for a cross-section of 74 patients with unilateral ACL tears. Tibial subluxation and coronal limb alignment were measured on hip-to-ankle weightbearing radiographs. Eight cadaveric knees were mounted on a 6 degree of freedom robot. Mediolateral position and varus-valgus alignment of the tibia relative to the femur were measured in response to 300-N axial compression simulating quiet standing at 5° and 15° of flexion with the ACL intact and sectioned. RESULTS: Across all 74 patients included in the clinical study, the ACL-injured knee experienced 1.6 ± 2.3 mm (mean ± SD) of medial tibial subluxation compared with the contralateral uninjured knee (P < .001). The 24 patients with isolated ACL rupture exhibited 2.0 ± 1.8 mm of medial subluxation (P < .001). The mean coronal alignment of all 74 patients in the study was 0.7° ± 2.8° varus in the injured limb and 1.3° ± 2.6° varus in the uninjured contralateral limb (P = .0187). In the cadaveric model, the tibia translated 0.4 ± 0.5 mm more medially after sectioning of the ACL at 15° of flexion (P = .0485); however, no changes in coronal alignment were detected. CONCLUSION: The tibia shifts medially and is less varus in the ACL-deficient knee on standing radiographs. The medial tibial shift is reproduced in an axially loaded cadaveric model. CLINICAL RELEVANCE: Medial tibiofemoral subluxation seen on frontal plane standing radiograph is an underappreciated sequela of isolated ACL rupture. The ability of ACL reconstruction to restore this aspect of ACL injury is not well understood and should be investigated further. Cadaveric models may be used to directly measure the mechanical effect of subtle changes in mediolateral position on articular contact stress as an indicator of the importance of this finding.

Medial Unicondylar Knee Arthroplasty Improves Patellofemoral Congruence: a Possible Mechanistic Explanation for Poor Association Between Patellofemoral Degeneration and Clinical Outcome.

The purpose was to determine the effect of medial fixed bearing unicondylar knee arthroplasty (UKA) on postoperative patellofemoral joint (PFJ) congruence and analyze the relationship of preoperative PFJ degeneration on clinical outcome. We retrospectively reviewed 110 patients (113 knees) who underwent medial UKA. Radiographs were evaluated to ascertain PFJ degenerative changes and congruence. Clinical outcomes were assessed preoperatively and postoperatively. The postoperative absolute patellar congruence angle (10.05 ± 10.28) was significantly improved compared with the preoperative value (14.23 ± 11.22) (P = 0.0038). No correlation was found between preoperative PFJ congruence or degeneration severity, and WOMAC scores at two-year follow up. Pre-operative PFJ congruence and degenerative changes do not affect UKA clinical outcomes. This finding may be explained by the post-op PFJ congruence improvement.

Role of magnetic resonance imaging in the diagnosis of the painful unicompartmental knee arthroplasty.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) is a well established method for the treatment of single compartment arthritis; however, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. This study investigates the effectiveness of magnetic resonance imaging (MRI) in guiding the diagnosis of the painful unicompartmental knee arthroplasty. METHODS: An IRB-approved retrospective review identified 300 consecutive UKAs performed over a three years period with 28 cases of symptomatic UKA (nine percent) with normal radiographic images. RESULTS: MRI examination was instrumental in finding a diagnosis that went undetected on radiographs. Based on MRI findings, 10 (36%) patients underwent surgery whilst 18 (64%) were treated conservatively. CONCLUSION: This study supports the use of MRI as a valuable imaging modality for managing symptomatic unicompartmental knee arthroplasty. LEVEL OF EVIDENCE: Case series.

Lower limb alignment control: is it more challenging in lateral compared to medial unicondylar knee arthroplasty?

INTRODUCTION: Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on outcomes. The literature lacks lateral UKA alignment studies, making our understanding of this issue based on medial UKA. METHODS: We evaluated limb alignment in 241 patients who underwent medial (229 knees) or lateral (37 knees) UKA. Alignment was measured pre and postoperatively in radiographs and intra-operatively using a navigation system. We compared the percentage of over-correction and the difference between post-operative alignment and navigation measurement. RESULTS: Percentage of overcorrection was significantly higher in the lateral UKAs (11%) compared to the medial UKAs (4%). In medial UKAs, the mean difference between the intraoperative alignment and the post-operative was 1.33°. This was significantly lower than the mean 1.86° difference in the lateral UKAs. CONCLUSIONS: Our data demonstrated an increased risk of "overcorrection," and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs.

Onlay tibial implants appear to provide superior clinical results in robotic unicompartmental knee arthroplasty.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) is an increasingly popular option for the treatment of single-compartment knee osteoarthritis (OA) in adults. Two options for tibial resurfacing during UKA are (1) all-polyethylene inlays and (2) metal-backed onlays. QUESTIONS/PURPOSES: The aim of this study was to determine whether there are any differences in clinical outcomes with inlay versus onlay tibial components. PATIENTS AND METHODS: We identified 39 inlays and 45 onlays, with average 2.7- and 2.3-year follow-up, respectively, from a prospective robotic-assisted surgery database. The primary outcome was the Western Ontario and McMaster University Arthritis Index (WOMAC), subcategorized by the pain, stiffness, and function subscores, at 2 years postoperatively. The secondary outcome was the need for secondary or revision surgery. RESULTS: Postoperative WOMAC pain score was 3.1 for inlays and 1.6 for onlays (p = 0.03). For 25 inlays and 30 onlays with both preoperative and postoperative WOMAC data, pain score improved from 8.3 to 4.0 for inlays versus from 9.2 to 1.7 for onlays (p = 0.01). Function score improved from 27.5 to 12.5 for inlays versus from 32.1 to 7.3 for onlays (p = 0.03). Four inlays and one onlay required a secondary or revision procedure (p = 0.18). CONCLUSIONS: We advise using metal-backed onlays during UKA to improve postoperative clinical outcomes.

Limb alignment, subluxation, and bone density relationship in the osteoarthritic varus knee.

Lower limb alignment, tibiofemoral (TF) subluxation, and bone density changes around the knee are significant factors related to the development of knee osteoarthritis (OA) and have great impact on its severity. The relation of each factor to knee OA was evaluated separately in previous studies; however, few studies have attempted to integrate their respective effects. The purpose of this study was to determine if an identifiable interaction exists between coronal limb alignment, TF subluxation, and bone density in the development of knee OA. A total of 120 patients with symptomatic, varus knee OA, with preoperative standing anteroposterior (AP) hip-to-ankle radiographs and a computed tomographic scan of the knee, were included in this study. Overall mechanical lower extremity alignment, and TF subluxation were measured on the AP radiographs, while trabecular bone density (TBD) was measured in four regions of interest for both the tibial plateau and distal femur in all patients. The patients were stratified into the following four cohorts: (A) high subluxation, high angulation; (B) high subluxation, low angulation; (C) low subluxation, high angulation; and (D) low subluxation, low angulation. The mean TBD in group B was significantly higher than in groups C and D (p = 0.003 and 0.03, respectively). In addition, the mean TBD in group A was significantly higher than in group C. This study highlights the relationship between limb alignment, knee subluxation, and bone density in the osteoarthritic knee. These preliminary results present a proof-of-principle, that bone mineral density affects the degree of coronal alignment and TF subluxation in OA.

Lateral robotic unicompartmental knee arthroplasty.

Robotic-assisted unicompartmental knee arthroplasty (UKA) is accurate and repeatable. Lateral UKA is still considered a challenge, as the lateral side of the knee has different anatomy and kinematics compared with the medial side. The lateral compartment of the knee is less constrained than the medial compartment and is therefore less tolerant for mobile-bearing implants and ACL deficiency. However, the long-term outcomes of lateral UKA are scarce. Moreover, the impact of patellofemoral joint degeneration on the outcome of lateral UKA is unknown. We report our preliminary results with fixed bearing robotic-assisted lateral UKA, which are encouraging in the short term.

Notchplasty in anterior cruciate ligament reconstruction in the setting of passive anterior tibial subluxation.

PURPOSE: In an effort to minimize graft impingement among various ACL deficient states, we sought to quantitatively determine requirements for bone resection during notchplasty with respect to both volumetric amount and location. METHODS: A validated method was used to evaluate Magnetic Resonance Imaging scans. We measured the ATT of the medial and lateral compartments in the following four states: intact ACL (27 patients), acute ACL disruption; <2 months post-injury (76 patients), chronic ACL disruption; 12 months post-injury (42 patients) and failed ACL reconstruction (75 patients). Subsequently, 11 cadaveric knees underwent Computed Tomography (CT) scanning. Specialized software allowed virtual anterior translation of the tibia according to the average ATT measured on MRI. Impingement volume was analyzed by performing virtual ACLRs onto the various associated CT scans. Location was analyzed by overlaying an on-screen protractor. The center of the notch was defined as 0°. RESULTS: Average impingement volume changed significantly in the various groups compared to the intact ACL group (acute 577 ± 200 mm(3), chronic 615 ± 199 mm(3), failed ACLR 678 ± 210 mm(3), p=0.0001). The location of the required notchplasty of the distal femoral wall border did not change significantly. The proximal femoral border moved significantly towards the center of the notch (acute 8.6° ± 4.8°, chronic 7.8° ± 4.2° (p=0.013), failed ACLR 5.1° ± 5.9° (p=0.002)). CONCLUSION: Our data suggests that attention should be paid peri-operatively to the required volume and location of notchplasty among the various ACL deficient states to minimize graft impingement.

Neglected rotatory knee dislocation: A case report.

UNLABELLED: We report here a unique case of a 3 year neglected rotatory tibiofemoral dislocation associated with a lateral patellar dislocation. The rotational deformity was gradually corrected using a Taylor spatial frame and the patella was realigned by tibial tubercle osteotomy and transfer. The patient also underwent multiple soft tissue releases and quadricepsplasty to improve knee flexion. At nine year follow-up, the patient has good knee range of motion, a congruent knee joint and a good functional result. CLINICAL RELEVANCE: Taylor spatial frame combined with other orthopedic approaches can be a useful tool while dealing with neglected knee dislocations.

Coronal tibiofemoral subluxation: a new measurement method.

BACKGROUND: Coronal tibiofemoral (CTF) subluxation is a common finding in knee osteoarthritis (OA) which can be related to poor pain scores and tibial spine impingement. In this study we describe a new method for measuring CTF subluxation and present validation of the method using cadaveric knees. METHODS: A prototype software code based on the ICP mathematical algorithm was developed to measure CTF subluxation; the code finds the rigid transformation that best aligns the articular surfaces, measures CTF subluxation and the angle between articular surfaces. For validation, three stripped fresh frozen cadaveric knee specimens were transfixed to a specially designed knee fixation device where tibiofemoral angle and CTF subluxation can be measured directly. Fluoroscopic images were obtained with the tibiofemoral joint in neutral alignment and with 5, 10 and 15 (mm) of medial and lateral subluxation. This procedure was repeated with a neutral tibiofemoral angle, 10° of varus and 10° of valgus. All images were analyzed independently by two investigators using the prototype software. RESULTS: The interclass correlation coefficient between the two investigators for CTF subluxation and tibiofemoral angle was 0.93 and 0.99 respectively. The CTF subluxation and tibiofemoral angle measured by the software correlated to the CTF subluxation and tibiofemoral angle were defined using the knee fixation device, with Pearson product moments of 0.86 and 0.94 respectively. CONCLUSION: Our suggested prototype software is precise, repeatable and reliable at measuring CTF subluxation and tibiofemoral angle. It may prove to be a useful tool to evaluate CTF subluxation in a clinical setting.

Is tibiofemoral subluxation correctable in unicompartmental knee arthroplasty?

The purposes of this study were to describe a method for measuring tibiofemoral subluxation in UKA, and to report the mean amount of tibiofemoral subluxation seen both preoperatively and postoperatively in a cohort of patients undergoing UKA. Two hundred thirty-five patients who received a medial UKA, and 39 patients who received a lateral UKA, were reviewed. In the medial UKA cohort, the mechanical alignment was corrected from 7.7° ± 5.9° preoperatively, to 2.9° ± 2.5° postoperatively, while the tibiofemoral subluxation was corrected from 4.5 mm ± 3.0 mm preoperatively, to 2.3 mm ± 2.7 mm postoperatively. In the lateral UKA cohort, the mechanical alignment was corrected from -5.5° ± 3.8° to -1.6° ± 3.4°, while the tibiofemoral subluxation was corrected from 4.3 mm ± 2.7 mm to 2.8 mm ± 2.5mm. This study presents a novel method for measurement of tibiofemoral subluxation, the mean amount of tibiofemoral subluxation present preoperatively, and the amount of correction that can be expected during both medial and lateral unicondylar knee arthroplasty.