Changes In Posterior Condylar Offset Research Articles

Increased Posterior Condylar Offset Decreases the Extension Gap in Cases With Flexion Contracture in Modified Gap Technique Total Knee Arthroplasty.

Purpose There have been no reports comparing the change in medial and lateral posterior condylar offset (PCO) and the extension gaps. The purpose of this study was to elucidate the relationship between the change in medial and lateral PCO and the extension gap in total knee arthroplasty (TKA). The hypothesis is that an increase in both medial and lateral PCO can be a factor for a decrease in the extension gap, especially in cases of flexion contracture. Methods This retrospective study included 63 patients with medial osteoarthritis who underwent mobile-bearing PS-TKA using the modified gap techniques. Patients consisted of seven men (seven knees) and 53 women (56 knees), with the mean age of 76 (range, 58-88) years. The patients with valgus knee and cruciate retaining TKA were excluded. The medial ΔPCO (ΔPCO defined as the amount of change of the PCO before the resection of the posterior condyle and after the implant setting), lateral ΔPCO, the rotation angle of the posterior condyle osteotomy, and the gap differences were evaluated. The data were compared among three groups（Group A: ΔPCO increase on both sides, Group B: ΔPCO increase on only one side, Group C: ΔPCO decrease on both sides. The gap differences were compared between the cases with flexion contracture of ≥ 15° and the cases with flexion contracture of < 15°.The correlations between the gap differences and flexion contracture were evaluated in each group. Results There was no gap difference evident in any group (P≥0.05). The gap difference in Groups A (P=0.0067) and group C (P=0.0484) was significantly larger in cases with flexion contracture of ≥ 15° compared to those with flexion contracture of < 15°. Conclusions There was no correlation between the change in PCO and the extension gap. However, there was an inverse correlation between the flexion contracture and extension gap in cases with increased medial and lateral PCO.

Risk factors of de novo hyperextension developed after posterior cruciate ligament substituting total knee arthroplasty: a matched case-control study.

To investigate factors contributing to the de novo hyperextension after posterior cruciate ligament substituting (PS) total knee arthroplasty (TKA). Through a retrospective case-control study, de novo hyperextension patients were compared with patients without hyperextension after primary PS TKA. Eighty-five hyperextension patients were compared with 85 patients in a control group matched by age, sex, surgeon and implant. The clinical and radiographic parameters, including the mechanical axis (MA), joint line convergence angle (JLCA), posterior tibial slope angle (PTSA), posterior condylar offset (PCO), and the gamma angle, were evaluated preoperatively and immediate postoperatively. Comparisons between the two groups and logistic regression analysis were performed to investigate factors contributing to de novo hyperextension. Among the clinical factors, preoperative flexion contracture was less (5° ± 6° vs. 11° ± 6°, p < 0.001) and the range of motion was greater (125° ± 12° vs. 118° ± 5°, p = 0.041) in the de novo hyperextension group than in the control group. Among the radiographic parameters, preoperative and postoperative JLCA were greater (8.1° ± 4.4° vs. 6.1° ± 3.5°, p < 0.001, 1.0° ± 1.3° vs. 0.2° ± 0.8°, p = 0.002, respectively), postoperative PTSA was greater (3.7° ± 2.0° vs. 3.3° ± 1.6°, p < 0.001) and preoperative and postoperative PCO were less in the hyperextension group than in the control group (26.3mm ± 3.3mm vs. 29.1mm ± 3.2mm, p < 0.001, 26.4mm ± 3.2mm vs. 29.1mm ± 3.0mm, p < 0.001, respectively), whereas, change in PCO was greater in the hyperextension group (1.1mm ± 7.7mm vs. - 0.1mm ± 3.3mm, p < 0.001). In multivariate analysis, the degree of medial soft tissue release [odds ratio (OR) 2.83, p = 0.003], flexion contracture [OR 0.86, p = 0.028], postoperative JLCA [OR 2.45, p = 0.004], preoperative PCO and a change in PCO [OR 0.74, p = 0.002, OR 1.89, p = 0.001, respectively] were the factors associated with de novo hyperextension. An increased degree of medial soft tissue release, small preoperative flexion contracture, increased postoperative JLCA, decreased preoperative PCO and increased change in PCO were risk factors of de novo hyperextension. III.

Risk factors of hyperextension and its relationship with the clinical outcomes following mobile-bearing total knee arthroplasty.

To evaluate the incidence and risk factors of postoperative hyperextension after mobile-bearing total knee arthroplasty (TKA) and its clinical outcomes. This retrospective case-control study included 387 knees of primary TKA patients after a 5-year follow-up. The clinical outcomes and radiographs including posterior condylar offset (PCO), femur and tibial slope angle and its discrepancy were evaluated. The patients were divided into two groups (group 1: non-hyperextension, group 2: hyperextension). An extension greater than 5° measured using a goniometer at the final follow-up was defined as hyperextension. Logistic and linear regression analyses were performed. Overall, 43 knees (11.1%) with hyperextension were observed at the last follow-up. There was no significant difference between groups in terms of the clinical outcomes although the functional scores were worse in group 2. There was no significant difference in the postoperative radiologic evaluation except for a change in PCO (group 1 vs. group 2; -0.2mm ± 3.8 vs. -2.4mm ± 3.0, p = 0.003), distal femoral resection slope angle (-9.1° ± 2.1 vs. -12.1° ± 1.7, p < 0.000) and discrepancy of the slope angle (0.3° ± 4.5 vs. -3.6° ± 3.9, p < 0.000). The change in PCO [odds ratio (OR) 0.86, p = 0.012], discrepancy of the slope angle (OR 0.8136, p = 0.000) and the preoperative mechanical femorotibial angle (OR 1.09, p = 0.003) were associated with hyperextension. Mobile-bearing TKA with hyperextension over 5° showed worse functional outcomes at the mid-term follow-up, even though no serious complications were observed. Care should be taken to maintain the posterior condylar offset and to match the resection angles in femur and tibia due to the risk of hyperextension and worse functional outcomes. IV.

Biomechanical analysis of a changed posterior condylar offset under deep knee bend loading in cruciate-retaining total knee arthroplasty.

The conservation of the joint anatomy is an important factor in total knee arthroplasty (TKA). The restoration of the femoral posterior condylar offset (PCO) has been well known to influence the clinical outcome after TKA. The purpose of this study was to determine the mechanism of PCO in finite element models with conservation of subject anatomy and different PCO of ±1, ±2, ±3mm in posterior direction using posterior cruciate ligament-retaining TKA. Using a computational simulation, we investigated the influence of the changes in PCO on the contact stress in the polyethylene (PE) insert and patellar button, on the forces on the collateral and posterior cruciate ligament, and on the quadriceps muscle and patellar tendon forces. The computational simulation loading condition was deep knee bend. The contact stresses on the PE insert increased, whereas those on the patellar button decreased as posterior condylar offset translated to the posterior direction. The forces exerted on the posterior cruciate ligament and collateral ligaments increased as PCO translated to the posterior direction. The translation of PCO in the anterior direction, in an equivalent flexion angle, required a greater quadriceps muscle force. Translations of the PCO in the posterior and anterior directions resulted in negative effects in the PE insert and ligament, and the quadriceps muscle force, respectively. Our findings suggest that orthopaedic surgeons should be careful with regard to the intraoperative conservation of PCO, because an excessive change in PCO may lead to quadriceps weakness and an increase in posterior cruciate ligament tension.

Interactive effect of femoral posterior condylar offset and tibial posterior slope on knee flexion in posterior cruciate ligament-substituting total knee arthroplasty

BackgroundThis work aimed to evaluate the changes in the femoral posterior condylar offset (PCO) and tibial slope after posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA), and to address the presence of any interactive effect between the two on knee flexion. MethodsFifty-two PCL-substituting TKAs were performed using a posterior referencing system. Three-dimensional reconstructed computed tomographic (CT) images were used to evaluate PCO and tibial slope before and after arthroplasty. Range of motion and clinical scores were evaluated at a mean of 3.1years postoperatively. Multivariate linear model with interaction terms was used to evaluate and compare the relationships among changes in PCO, tibial slope, and postoperative knee flexion angles. ResultsThe degree of change in PCO was greater in the lateral condyle than in the medial condyle (3.1±2.5mm and −0.5±2.8mm, respectively). Postoperative medial and lateral tibial slopes were 1.4°±1.8 and 1.4°±2.0, respectively. The mean degree of postoperative knee flexion was 125°. Analysis with interaction terms and covariate adjustment demonstrated that medial PCO and tibial slope were significantly related to knee flexion with interactive effect (P=0.011). In cases with <3° posterior tibial slope, the postoperative PCO was positively correlated to the degree of knee flexion angle. However, in cases with >3° tibial slope, PCO was negatively correlated to knee flexion. ConclusionMedial femoral PCO and tibial slope showed interactive effect on knee flexion after PCL-substituting TKAs. Reconstitution of the proper PCO and avoiding excessive tibial slope may be necessary.

A computational simulation study to determine the biomechanical influence of posterior condylar offset and tibial slope in cruciate retaining total knee arthroplasty

ObjectivesPosterior condylar offset (PCO) and posterior tibial slope (PTS) are critical factors in total knee arthroplasty (TKA). A computational simulation was performed to evaluate the biomechanical effect of PCO and PTS on cruciate retaining TKA.MethodsWe generated a subject-specific computational model followed by the development of ± 1 mm, ± 2 mm and ± 3 mm PCO models in the posterior direction, and -3°, 0°, 3° and 6° PTS models with each of the PCO models. Using a validated finite element (FE) model, we investigated the influence of the changes in PCO and PTS on the contact stress in the patellar button and the forces on the posterior cruciate ligament (PCL), patellar tendon and quadriceps muscles under the deep knee-bend loading conditions.ResultsContact stress on the patellar button increased and decreased as PCO translated to the anterior and posterior directions, respectively. In addition, contact stress on the patellar button decreased as PTS increased. These trends were consistent in the FE models with altered PCO. Higher quadriceps muscle and patellar tendon force are required as PCO translated in the anterior direction with an equivalent flexion angle. However, as PTS increased, quadriceps muscle and patellar tendon force reduced in each PCO condition. The forces exerted on the PCL increased as PCO translated to the posterior direction and decreased as PTS increased.ConclusionThe change in PCO alternatively provided positive and negative biomechanical effects, but it led to a reduction in a negative biomechanical effect as PTS increased.Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, J-S. Lee, S. K. Kwon. A computational simulation study to determine the biomechanical influence of posterior condylar offset and tibial slope in cruciate retaining total knee arthroplasty. Bone Joint Res 2018;7:69–78. DOI: 10.1302/2046-3758.71.BJR-2017-0143.R1.

Does Posterior Condylar Offset Affect Clinical Results following Total Knee Arthroplasty?

Total knee arthroplasty (TKA) is an effective, durable treatment for knee osteoarthritis. However, a subset of patients experiences incomplete pain relief and ongoing dysfunction. Posterior condylar offset (PCO) has previously been shown to be associated with postoperative range of motion (ROM) following TKA; however, an association with patient-reported outcome measures (PROMs) has not been established. The purpose of this study was to evaluate the association between PCO and postoperative ROM and PROMs. A retrospective review of 970 posterior-stabilized single design TKAs was performed. Preoperative and postoperative radiographs were analyzed to measure the change in PCO and anteroposterior (AP) femoral dimension. Clinical outcome measures, including Short Form-12 physical and mental component summaries, Western Ontario and McMaster Universities Arthritis Index, and Knee Society Score were reviewed to determine if these were influenced by changes in PCO and AP dimension. PCO was increased by more than 3 mm in 15.1%, maintained (within 3 mm) in 59.6%, and decreased by more than 3 mm in 25.3% of patients. Comparing between these groups, there were no significant differences in postoperative ROM or PROM. AP dimension increased in 24.4%, maintained in 47.8%, and decreased in 27.8%. Similarly, there were no significant differences in ROM or PROM between these groups. Spearman's correlation analyses failed to identify an association between PCO and ROM or PROMs. In conclusion, increasing or decreasing PCO or AP femoral dimension with this PS TKA design did not significantly affect postoperative ROM or PROM. Similarly, maintenance of PCO within one implant size with this system compared with optimal sizing had no deleterious effect on TKA outcomes.

Effect of the Referencing System on the Posterior Condylar Offset and Anterior Flange-Bone Contact in Posterior Cruciate-Substituting Total Knee Arthroplasty

BackgroundThe effect of referencing system on posterior condylar offset (PCO) after total knee arthroplasty (TKA) is still controversial. Moreover, there is a lack of concern about the anterior flange-bone contact according to the referencing system. MethodsOne hundred four TKAs using the anterior referencing (AR) system and 107 TKAs using the posterior referencing (PR) system were analyzed with 2-year follow-up. The PCO, PCO ratio (PCOR), and contact at the anterior flange-bone interface were compared between the 2 groups. The flexion and extension gaps and the degree of medial release were measured, and clinical outcomes were evaluated. Finally, the correlation between changes in PCO and knee flexion angle was analyzed. ResultsThe mean postoperative PCO and PCOR were significantly larger in the PR group than in the AR group. Incomplete contact between the anterior flange and anterior femur occurred more frequently in the AR group than in the PR group (48.1% vs 13.1%, P < .001). The medial and lateral flexion gaps were significantly larger in the AR group than in the PR group. The groups showed no differences in soft tissue release, degree of flexion, and clinical scores. In both groups, there was no correlation between postoperative change of PCO and improvement in flexion. ConclusionThe PR system produced larger PCO and PCOR, and smaller flexion gap compared to the AR system. Additionally, the PR group showed more favorable contact between the anterior flange and anterior femur. However, these differences were not related to the degree of soft tissue release and clinical outcomes.

Biomechanical Effects of Posterior Condylar Offset and Posterior Tibial Slope on Quadriceps Force and Joint Contact Forces in Posterior-Stabilized Total Knee Arthroplasty.

This study aimed to determine the biomechanical effect of the posterior condylar offset (PCO) and posterior tibial slope (PTS) in posterior-stabilized (PS) fixed-bearing total knee arthroplasty (TKA). We developed ±1, ±2, and ±3 mm PCO models in the posterior direction and −3°, 0°, 3°, and 6° PTS models using a previously validated FE model. The influence of changes in the PCO and PTS on the biomechanical effects under deep-knee-bend loading was investigated. The contact stress on the PE insert increased by 14% and decreased by 7% on average as the PCO increased and decreased, respectively, compared to the neutral position. In addition, the contact stress on post in PE insert increased by 18% on average as PTS increased from −3° to 6°. However, the contact stress on the patellar button decreased by 11% on average as PTS increased from −3° to 6° in all different PCO cases. The quadriceps force decreased by 14% as PTS increased from −3° to 6° in all PCO models. The same trend was found in patellar tendon force. Changes in PCO had adverse biomechanical effects whereas PTS increase had positive biomechanical effects. However, excessive PTS should be avoided to prevent knee instability and subsequent failure.

Rôle de l’épaisseur du cartilage condylien postérieur dans le calcul de l’offset condylien. Influence sur la mobilité après prothèse totale du genou postéro-stabilisée

BackgroundThe association between posterior condylar offset (PCO) and maximal knee flexion remains controversial. The measured PCO in the previous studies is usually determined on the plain radiographs without taking into account the cartilage thickness. HypothesisFull-thickness cartilage-based PCO is a valid criterion to compare pre-operative and post-operative offset, and has a significant influence on post-operative knee flexion after total knee arthroplasty.Materials and methods: Ninety-five patients (107 knees) who underwent posterior-stabilized total knee arthroplasty were enrolled in a prospective study. Intra-operative measurement of cartilage thickness of the posterior femoral condyle was documented in all patients. Pre-operative and post-operative radiographic PCO was measured respectively on the true lateral view of the knee. True PCO was adjusted by adding cartilage thickness of the posterior femoral condyle. The relationship between the change in knee flexion and PCO difference was assessed using Pearson correlation analysis. ResultsThe post-operative radiographic PCO difference (2.01±2.05mm) was significantly greater than the true PCO difference (0.09±2.12mm). The mean post-operative change in maximum knee flexion angle was 5.4°±9.9°. No significant correlation was found between PCO difference and the change in knee flexion, regardless of radiographic (P=0.232) or cartilage-based measurements (P=0.693). ConclusionsFull-thickness cartilage-based PCO is an optimal criterion to estimate the change in PCO before and after total knee arthroplasty. However in this study, neither cartilage-based nor radiographic PCO appeared to have a significant influence on post-operative knee flexion after posterior-stabilized total knee arthroplasty. Level of evidenceLevel 4 cohort study.

Full-thickness cartilage-based posterior femoral condylar offset. Influence on knee flexion after posterior-stabilized total knee arthroplasty

BackgroundThe association between posterior condylar offset (PCO) and maximal knee flexion remains controversial. The measured PCO in the previous studies is usually determined on the plain radiographs without taking into account the cartilage thickness. HypothesisFull-thickness cartilage-based PCO is a valid criterion to compare preoperative and postoperative offset, and has a significant influence on postoperative knee flexion after total knee arthroplasty. Materials and methodsNinety-five patients (107 knees) who underwent posterior-stabilized total knee arthroplasty were enrolled in a prospective study. Intra-operative measurement of cartilage thickness of the posterior femoral condyle was documented in all patients. Preoperative and postoperative radiographic PCO was measured respectively on the true lateral view of the knee. True PCO was adjusted by adding cartilage thickness of the posterior femoral condyle. The relationship between the change in knee flexion and PCO difference was assessed using Pearson correlation analysis. ResultsThe postoperative radiographic PCO difference (2.01±2.05mm) was significantly greater than the true PCO difference (0.09±2.12mm). The mean postoperative change in maximum knee flexion angle was 5.4°±9.9°. No significant correlation was found between PCO difference and the change in knee flexion, regardless of radiographic (P=0.232) or cartilage-based measurements (P=0.693). ConclusionsFull-thickness cartilage-based PCO is an optimal criterion to estimate the change in PCO before and after total knee arthroplasty. However in this study, neither cartilage-based nor radiographic PCO appeared to have a significant influence on postoperative knee flexion after posterior-stabilized total knee arthroplasty. Level of evidenceLevel 4 Cohort Study.

Do tibiofemoral contact point and posterior condylar offset influence outcome and range of motion in a mobile-bearing total knee arthroplasty?

The posterior condylar offset (PCO) and the tibiofemoral contact point (CP) have been reported as important factors that can influence range of motion and clinical outcome after total knee arthroplasty. A mobile-bearing knee implant with an anterior posterior gliding insert would in theory be more sensitive for changes in PCO and CP. For this reason, we analysed the PCO and CP and the relation with outcome and range of motion in 132 patients from a prospectively documented cohort in this type of implant. The prosthesis used was a posterior cruciate retaining AP gliding mobile-bearing total knee replacement (SAL II Sulzer Medica, Switzerland). In 132 knees, the pre- and postoperative PCO and postoperative CP were evaluated. Measurements were made on X-rays of the knee taken in approximately 90° of flexion and with less than 3-mm rotation of the femur condyles. The outcome parameters, range of motion (ROM) and the knee society score (KSS), for each knee were determined preoperatively and at 5-year follow-up. The mean KSS improved from 91 to 161 at 5-year follow-up (p < 0.001) and the mean ROM from 102 to 108 (p < 0.05). The mean PCO difference (postoperative PCO-preoperative PCO) was--0.05 mm (SD 2.15). The CP was on average 53.9% (SD 5.5%). ROM was different between the 3 PCO groups (p = 0.05): patients with 3 or more mm decrease in PCO had the best postoperative ROM (p = 0.047). There was no statistical difference between the postoperative ROM between patients with a stable PCO and those with an increased PCO. There was no correlation between the difference in PCO and the difference in ROM; R Pearson = -0.056. There was no difference in postoperative ROM or postoperative total KSS between CP <60% and CP >60%: p = 0.22, p = 0.99, for ROM and KSS, respectively. Scatter plots showed uniform clouds of values: increase or decrease in PCO and CP had no significant influence on ROM or KSS. The hypotheses that a stable PCO and a more natural CP increase postoperative ROM and improve clinical outcome could not be confirmed. On the contrary, a decreased PCO seemed to improve knee flexion. Furthermore, a relationship between PCO and CP could not be found. Prospective cohort study, Level II.

Changes in Posterior Condylar Offset After Total Knee Arthroplasty Cannot be Determined by Radiographic Measurements Alone

Restoration of femoral posterior condylar offset (PCO) may contribute to maximum flexion after total knee arthroplasty. Accurate radiographic measurement of postoperative PCO is possible, as the prosthesis margins can be easily identified; however, preoperative measurement of PCO may be inaccurate, as the remaining cartilage thickness of the posterior condyles is not included. This error may contribute to the controversy surrounding the importance of PCO. In this institutional review board–approved study, the cartilage thickness of posterior condylar specimens resected during total knee arthroplasty was measured. Mean cartilage thicknesses of the posterior condyles were 1.7 mm (range, 0-4 mm) medially and 2.0 mm (range, 0-5 mm) laterally. As the cartilage thickness is variable, future studies of PCO must adjust the preoperative radiographic measurements by the cartilage thickness measured intraoperatively.

Changes in the Medial and Lateral Posterior Condylar Offset in Total Knee Arthroplasty

The purpose of this study was to clarify the changes between preoperation and postoperation in each posterior condylar offset (PCO) using computed tomography (CT) and to compare them to conventional radiographic (x-ray) evaluation in total knee arthroplasty. One hundred nine knees in 97 patients were evaluated. The medial PCO was significantly larger before surgery. The lateral PCO was significantly larger after surgery. Changes in the PCO on x-ray showed no significant correlation with the changes observed in the CT-evaluated medial ( R = 0.028) and lateral PCO ( R = 0.190). Changes in PCO observed by x-ray did not reflect those of the medial or lateral condyles on CT. We recommend CT-based evaluation of PCO by condyle when assessing the influence of PCO on range of motion following total knee arthroplasty.