Aims. While residual fixed flexion deformity (FFD) in unicompartmental knee arthroplasty (UKA) has been associated with worse functional outcomes, limited evidence exists regarding FFD changes. The objective of this study was to quantify FFD changes in patients with medial unicompartmental knee arthritis undergoing UKA, and investigate any correlation with clinical outcomes. Methods. This study included 136 patients undergoing robotic arm-assisted medial UKA between January 2018 and December 2022. The study included 75 males (55.1%) and 61 (44.9%) females, with a mean age of 67.1 years (45 to 90). Patients were divided into three study groups based on the degree of preoperative FFD: ≤ 5°, 5° to ≤ 10°, and > 10°. Intraoperative optical motion capture technology was used to assess pre- and postoperative FFD. Clinical FFD was measured pre- and postoperatively at six weeks and one year following surgery. Preoperative and one-year postoperative Oxford Knee Scores (OKS) were collected. Results. Overall, the median preoperative navigated (NAV) FFD measured 6.0° (IQR 3.1 to 8), while the median postoperative NAV FFD was 3.0° (IQR 1° to 4.4°), representing a mean correction of 49.2%. The median preoperative clinical FFD was 5° (IQR 0° to 9.75°) for the entire cohort, which decreased to 3.0° (IQR 0° to 5°) and 2° (IQR 0° to 3°) at six weeks and one year postoperatively, respectively. A statistically significant improvement in PROMs compared with baseline was evident in all groups (p < 0.001). Regression analyses showed that participants who experienced a larger FFD correction, showed greater improvement in PROMs (β = 0.609, p = 0.049; 95% CI 0.002 to 1.216). Conclusion. This study found that UKA was associated with an approximately 50% improvement in preoperative FFD across all three examined groups. Participants with greater correction of FFD also demonstrated larger OKS gains. These findings could prove a useful augment to clinical decision-making regarding candidacy for UKA and anticipated improvements in FFD

Fixed flexion deformities are common in osteoarthritic knees that are indicated for total knee arthroplasty. The lack of full extension at the knee results in a greater force of quadriceps contracture and energy expenditure. It also results in slower walking velocity and abnormal gait mechanics, overloading the contralateral limb. Residual flexion contractures after TKA have been associated with poorer functional scores and outcomes. Although some flexion contractures may resolve with time after surgery, a substantial percentage will become permanent. Therefore, it is essential to correct fixed flexion deformities at the time of TKA, and be vigilant in the post-operative course to maintain the correction. Surgical techniques to address pre-operative flexion contractures include: adequate bone resection, ligament releases, removal of posterior osteophytes, and posterior capsular releases. Post-operatively, extension can be maintained with focused physiotherapy, a specially modified continuous passive motion machine, a contralateral heel lift, and splinting

We investigated fixed flexion deformity (FFD) after total knee replacement (TKR). Data relating to 369 cruciate-retaining unilateral TKRs performed at a single institution were collected prospectively. Fixed flexion was measured pre-operatively and at one week, six months, 18 months, three years and five years after surgery. Using binary logistic regression, pre-operative FFD was a predictor of post-operative FFD > 10° at one week (p = 0.006) and six months (p = 0.003) following surgery. Gender was a predictor at one week (p = 0.0073) with 24% of women showing a FFD > 10° compared with 37% of men. We have shown that a gradual improvement in knee extension can be expected up to three years after surgery in knees with FFD. By this time residual FFD is mild or absent in the majority of patients, including those who had a severe pre-operative FFD

Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s correlation coefficient = 0.81; p < 0.001). PCL resection did not significantly affect limb alignment (mean change in alignment: 0.2° valgus (. sd. 1.2); p = 0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap more than the extension gap. The increase in the lateral flexion gap is greater than the increase in the medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity before PCL resection. Cite this article: Bone Joint J 2019;101-B:1230–1237

Abstract. Introduction. This study compared biomechanical and functional parameters of a total knee arthroplasty (TKA) implant (Cemented Zimmer Hi-Flex) against healthy older adults to determine whether knee biomechanics was restored in this patient population. Methodology. Patients with a primary TKA and healthy adults >55 years old with no musculoskeletal deficits or arthritis participated. Bilateral knee range of motion (RoM) was assessed with a goniometer, then gait patterns were analysed with a 3D motion-capture system. An arthrometer then quantified anterior-posterior laxity of each knee. Statistical analyses were performed in SPSS (α=0.05; required sample size: n=21 per group). Results. 25 knees were replaced in 21 patients. Nine presented with fixed flexion deformities (FFD) (13.3±5.6°). FFDs were abolished intraoperatively, and the average flexion increased from 124.8±9.1° to 130.9±5.8°. At 9.6±3.2 years postoperatively, the patients achieved poorer RoM than healthy controls (n=23); p<0.0001. These differences were due to limited flexion in the knee. Patients also failed to achieve the same degree of flexion as controls bilaterally during gait. No differences were observed during mid-flexion; a state that has been associated with instability (p=0.614). There were no differences between groups in knee laxity. Conclusion. Patients in this study had similar gait patterns to healthy older adults during mid-flexion, and were no more likely to exhibit anterior-posterior translation of the knee >7mm; a known risk factor of instability. However, the flexion range was poorer. This led to bilateral pathological knee flexion patterns during gait. Further research should identify the cause of these limitations

Introduction. The objective of this study was to assess the effect of PCL resection on flexion-extension gaps, mediolateral soft tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilised total knee arthroplasty (TKA). Methods. This prospective study included 110 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted posterior-stabilised TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps pre- and post-PCL resection in knee extension and 90 degrees knee flexion. This study included 54 males (49.1%) and 56 females (50.9%) with a mean age of 68 ± 6.2 years at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1 ± 4.4 degrees varus. Results. PCL resection increased the flexion gap more than the extension gap in the medial (2.4 ± 1.5mm vs 1.3 ± 1.0mm respectively, p<0.001) and lateral (3.3 ± 1.6mm vs 1.2 ± 0.9mm respectively, p<0.01) compartments. The gap differences following PCL resection created mediolateral laxity in flexion (gap difference: 1.1 ± 2.5mm, p<0.001) but not in extension (gap difference: 0.1 ± 2.1mm, p=0.51). PCL resection improved overall FFD (6.3 ± 4.4° preoperatively vs 3.1 ± 1.5° postoperatively, p<0.001). There was a strong positive correlation between preoperative FFD and change in FFD following PCL release (Pearson correlation coefficient = 0.81, p<0.001). PCL resection did not affect overall limb alignment (change in alignment: 0.2 ± 1.2 degrees valgus, p=0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap proportionally more than the extension gap. The increase in the lateral flexion gap is greater than the increase in medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity prior to PCL resection. Bone resection, implant positioning, and periarticular soft tissue balancing should account for these changes in flexion-extension gaps, mediolateral laxity, and fixed flexion deformity following PCL resection in PS TKA. For figures, tables, or references, please contact authors directly

Aims. The objectives of this study were to assess the effect of anterior cruciate ligament (ACL) resection on flexion-extension gaps, mediolateral soft tissue laxity, maximum knee extension, and limb alignment during primary total knee arthroplasty (TKA). Methods. This prospective study included 140 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess study outcomes pre- and post-ACL resection with knee extension and 90° knee flexion. This study included 76 males (54.3%) and 64 females (45.7%) with a mean age of 64.1 years (SD 6.8) at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1° varus (SD 4.6° varus). Results. ACL resection increased the mean extension gap significantly more than the flexion gap in the medial (mean 1.2 mm (SD 1.0) versus mean 0.2 mm (SD 0.7) respectively; p < 0.001) and lateral (mean 1.1 mm (SD 0.9) versus mean 0.2 mm (SD 0.6) respectively; p < 0.001) compartments. The mean gap differences following ACL resection did not create any significant mediolateral soft tissue laxity in extension (gap difference: mean 0.1 mm (SD 2.4); p = 0.89) or flexion (gap difference: mean 0.2 mm (SD 3.1); p = 0.40). ACL resection did not significantly affect maximum knee extension (change in maximum knee extension = mean 0.2° (SD 0.7°); p = 0.23) or fixed flexion deformity (mean 4.2° (SD 3.2°) pre-ACL release versus mean 3.9° (SD 3.7°) post-ACL release; p = 0.61). ACL resection did not significantly affect overall limb alignment (change in alignment = mean 0.2° valgus (SD 1.0° valgus; p = 0.11). Conclusion. ACL resection creates flexion-extension mismatch by increasing the extension gap more than the flexion gap. However, gap differences following ACL resection do not create any mediolateral soft tissue laxity in extension or flexion. ACL resection does not affect maximum knee extension or overall limb alignment. Cite this article: Bone Joint J 2020;102-B(4):442–448

Aims. The purpose of this study was to report the experience of dynamic intraligamentary stabilisation (DIS) using the Ligamys device for the treatment of acute ruptures of the anterior cruciate ligament (ACL). Patients and Methods. Between March 2011 and April 2012, 50 patients (34 men and 16 women) with an acute rupture of the ACL underwent primary repair using this device. The mean age of the patients was 30 years (18 to 50). Patients were evaluated for laxity, stability, range of movement (ROM), Tegner, Lysholm, International Knee Documentation Committee (IKDC) and visual analogue scale (VAS) scores over a follow-up period of two years. Results. At final follow-up, anteroposterior translation differed from the normal knee by a mean of 0.96 mm (-2 mm to 6 mm). Median (interquartile range) IKDC, Tegner, Lysholm and VAS scores were 98 (95 to 100), 6 (5 to 7), 100 (98 to 100) and 10 (9 to 10), respectively. Pre-injury Tegner activity levels were reached one year post-operatively. A total of nine patients (18%) required a secondary intervention; five developed instability, of whom four underwent secondary hamstring reconstructive surgery, and five required arthroscopic treatment for intra-articular impingement due to scar tissue which caused a fixed flexion deformity. In addition, 30 patients (60%) required removal of the tibial screw. Conclusion. While there was a high rate of secondary interventions, 45 patients (90%) retained their repaired ACL two years post-operatively, with good clinical scores and stability of the knee. Take home message: Dynamic intraligamentary stabilisation presents a promising treatment option for acute ACL ruptures, eliminating the need for ACL reconstruction. Cite this article: Bone Joint J 2016;98-B:793–8

Aims

Total knee arthroplasty (TKA) with a highly congruent condylar-stabilized (CS) articulation may be advantageous due to increased stability versus cruciate-retaining (CR) designs, while mitigating the limitations of a posterior-stabilized construct. The aim was to assess ten-year implant survival and functional outcomes of a cemented single-radius TKA with a CS insert, performed without posterior cruciate ligament sacrifice.

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Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up.

Between June 1993 and December 1994, we performed total knee arthroplasty (TKA) on 27 knees in 24 patients with spontaneous bony ankylosis in severe flexion. The mean age at operation was 43.5 years (30 to 60). No patient had preoperative pain. Three were unable to walk and 21 could manage less than five blocks. The mean duration of the ankylosis was 18.7 years (13 to 25) and its mean position was 105° flexion (75 to 135). The preoperative Hospital for Special Surgery Knee Score of 60 points was improved to 87 at the final follow-up three to five years later. All knees were free from pain. The mean range of active flexion in 24 knees was 97° (78 to 115) and the mean arc of movement 91° (78 to 98). The mean fixed flexion deformity was 6° (0 to 25) and the extension lag 8° (0 to 25). Angular deformity was corrected to between 0° and 10° of valgus. Four patients were able to walk one block and 20 five to seven blocks. Thirteen knees (48%) showed some necrosis at the skin edge; one knee required arthrodesis and another resection arthroplasty. One had a recurrence of tuberculous infection requiring arthrodesis. One patient had a rupture of the quadriceps tendon. To date no prosthesis has required revision for loosening. Radiolucency of 1 mm or less about the tibial prosthesis was observed at follow-up in four of the 24 knees. Our results have shown that one-stage TKA and skeletal traction after operation can achieve correction of severe flexion deformity of the knee with marked improvement in the function and quality of life

Aims

The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA).

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The aim of this study was to compare any differences in the primary outcome (biphasic flexion knee moment during gait) of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) at one year post-surgery.

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Higher osteoblastic bone activity is expected in aseptic loosening and painful unicompartmental knee arthroplasty (UKA). However, insights into normal bone activity patterns after medial UKAs are lacking. The aim of this study was to identify the evolution in bone activity pattern in well-functioning medial mobile-bearing UKAs.

Aims

Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology.

Aims

Modern total knee arthroplasty (TKA) prostheses are designed to restore near normal kinematics including high flexion. Kneeling is a high flexion, kinematically demanding activity after TKA. The debate about design choice has not yet been informed by six-degrees-of-freedom in vivo kinematics. This prospective randomized clinical trial compared kneeling kinematics in three TKA designs.

Aims

An algorithm to determine the constitutional alignment of the lower limb once arthritic deformity has occurred would be of value when undertaking kinematically aligned total knee arthroplasty (TKA). The purpose of this study was to determine if the arithmetic hip-knee-ankle angle (aHKA) algorithm could estimate the constitutional alignment of the lower limb following development of significant arthritis.

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Our objective is to describe our early and mid-term results with the use of a new simple primary knee prosthesis as an articulating spacer in planned two-stage management for infected knee arthroplasty. As a second objective, we compared outcomes between the group with a retained first stage and those with a complete two-stage revision.

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It remains controversial whether patellofemoral joint pathology is a contraindication to lateral unicompartmental knee arthroplasty (UKA). This study aimed to evaluate the effect of preoperative radiological degenerative changes and alignment on patient-reported outcome scores (PROMs) after lateral UKA. Secondarily, the influence of lateral UKA on the alignment of the patellofemoral joint was studied.

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The aims of this study were to determine the effect of osteophyte excision on deformity correction and soft tissue gap balance in varus knees undergoing computer-assisted total knee arthroplasty (TKA).