No Difference in Postoperative Knee Flexion and Patient Joint Awareness Between Cruciate-Substituting and Cruciate-Retaining Medial Pivot Total Knee Prostheses: A 10-Year Follow-Up Study

No difference in clinical outcomes when retaining or sacrificing the posterior cruciate ligament in medial congruent total knee replacement. A retrospective study

PURPOSE

The aim of this study is to evaluate the effect of retaining or sacrificing the posterior cruciate ligament (PCL) in patients who undergo primary total knee replacement (TKR) with the medial congruent (MC) implant.

METHODS

This retrospective study looks at patients who underwent TKR with the MC implant. Comparison was made between the group with the PCL sacrificed (MC-PCLS) and the group with the PCL retained (MC-PCLR). Range of motion (ROM), Oxford knee score (OKS), Knee society knee score (KS-KS) and Knee society function score (KS-FS) were recorded.

RESULTS

The study identified 76 patients. 50 in the MC-PCLS group and 26 in the MC-PCLR group. Both groups had similar patient demographics. Three months postoperatively, OKS and KS-KS had significant improvement. However, there was significant improvement in KS-FS score in the MC-PCLS group but not the MC-PCLR group (MC-PCLR: 33 ± 17, p = 0.07; MC-PCLS: 19 ± 24, p = 0.01). Twelve months postoperatively, the OKS continued to improve significantly for both groups, while the KS-FS and KS-KS scores appeared to stagnate. The ROM continued to improve significantly for the MC-PCLR group but not the MC-PCLS group (MC-PCLR: 7 ± 9, p = 0.03; MC-PCLS: 4 ± 9, p = 0.30). Both groups were similar in ROM, OKS and KSS scores at both the 3 and 12 month post-operative period.

CONCLUSION

There is no difference in post-operative outcomes with the PCL retained or sacrificed. As such, surgeons can consider routinely sacrificing the PCL for easier balancing of the knee and shorter surgical time.

Tibial insert design significantly alters knee kinematics using a single cruciate-retaining total knee implant

Aims

Patient dissatisfaction is not uncommon following primary total knee arthroplasty. One proposed method to alleviate this is by improving knee kinematics. Therefore, we aimed to answer the following research question: are there significant differences in knee kinematics based on the design of the tibial insert (cruciate-retaining (CR), ultra-congruent (UC), or medial congruent (MC))?

Methods

Overall, 15 cadaveric knee joints were examined with a CR implant with three different tibial inserts (CR, UC, and MC) using an established knee joint simulator. The effects on coronal alignment, medial and lateral femoral roll back, femorotibial rotation, bony rotations (femur, tibia, and patella), and patellofemoral length ratios were determined.

Results

No statistically significant differences were found regarding coronal alignment (p = 0.087 to p = 0.832). The medial congruent insert demonstrated restricted femoral roll back (mean medial 37.57 mm; lateral 36.34 mm), while the CR insert demonstrated the greatest roll back (medial 42.21 mm; lateral 37.88 mm; p < 0.001, respectively). Femorotibial rotation was greatest with the CR insert with 2.45° (SD 4.75°), then the UC insert with 1.31° (SD 4.15°; p < 0.001), and lowest with the medial congruent insert with 0.8° (SD 4.24°; p < 0.001). The most pronounced patella shift, but lowest patellar rotation, was noted with the CR insert.

Conclusion

The MC insert demonstrated the highest level of constraint of these inserts. Femoral roll back, femorotibial rotation, and single bony rotations were lowest with the MC insert. The patella showed less shifting with the MC insert, but there was significantly increased rotation. While the medial congruent insert was found to have highest constraint, it remains uncertain if this implant recreates native knee kinematics or if this will result in improved patient satisfaction.

Tibiofemoral articulation and axial tibial rotation of the knee after a cruciate retaining total knee arthroplasty

PURPOSE

Numerous research has reported that total knee arthroplasty (TKA) cannot reproduce axial tibial rotations of normal knees. The objective of this study was to measure the tibiofemoral articular contact motions and axial tibial rotations of TKA knees to investigate the mechanism causing the knee kinematics change of after TKAs.

METHODS

Eleven patients with unilateral cruciate retaining (CR) TKA were tested for measurements of knee motion during a weight-bearing flexion from 0° to 105° using an imaging technique. The tibiofemoral contact kinematics were determined using the contact points on medial and lateral surfaces of the tibia and femoral condyles. Axial tibial rotations were calculated using the differences between the medial and lateral articulation distances on the femoral condyles and tibial surfaces at each flexion interval of 15°.

RESULTS

On femoral condyles, articular contact distances are consistently longer on the medial than on the lateral sides (p < 0.05) up to 60° of flexion, corresponding to internal tibial rotations (e.g., 1.3° ± 1.0° at 15-30° interval). On tibial surfaces, the articular contact point on the medial side moved more posteriorly than on the lateral side at low flexion angles, corresponding to external tibial rotations (e.g., -1.4° ± 1.8° at 15-30° interval); and more anteriorly than on the lateral sides at mid-range flexion, corresponding to internal tibial rotations (e.g., 0.8° ± 1.7° at 45-60° interval). At higher flexion, articular motions on both femoral condyles and tibial surfaces caused minimal changes in tibial rotations.

CONCLUSIONS

These results indicate that the axial tibial rotations of these TKA knees were mainly attributed to asymmetric articulations on the medial and lateral femoral condyles and tibial surfaces. The data can help understand the mechanisms causing axial tibial rotations of TKA knees and help improve implant designs for restoration of normal knee kinematics.

Simultaneous Post and Cone Fractures of a Polyethylene Insert in a Mobile-Bearing Posterior-Stabilized Total Knee Arthroplasty

We report a novel case of the simultaneous post and cone fractures of a polyethylene (PE) insert in a mobile-bearing posterior-stabilized total knee arthroplasty. Twelve years after the primary total knee arthroplasty, the 72-year-old male patient presented with a recurring right knee instability and was diagnosed with the wear of the PE insert based on physical and radiological examinations. Revision surgery was performed. The post and cone of the PE insert had fractured simultaneously. Moreover, the femoral and tibial components were in direct contact with each other. One year post-revision, knee function had improved. To diagnose a PE breakage, such as a post or cone fracture, surgeons should consider the possibility of PE breakage even in the absence of pain since patients might complain of subjective instability only.

Faster improvement in outcome scores in posterior stabilised total knee arthroplasty compared to medial congruent system with posterior cruciate ligament retained

Most studies comparing medial pivot to the posterior stabilised (PS) systems sacrifice the PCL. It is unknown whether retaining the PCL in the Medial Congruent (MC) system may provide further benefit compared to the more commonly used PS system. A retrospective review of a single-surgeon's registry data comparing 44 PS and 26 MC with PCL retained (MC-PCLR) TKAs was performed. Both groups had similar baseline demographics. The PS and MC-PCLR groups had similar pre-operative range of motion (ROM) (PS:104º ± 20º vs. MC-PCLR: 101º ± 19º, p = 0.70), Oxford Knee Score (OKS) (PS: 27 ± 6 vs. MC-PCLR: 26 ± 7, p = 0.62), and Knee Society Scoring System (KS) Function Score (KS-FS) (PS: 52 ± 24 vs. MC-PCLR: 56 ± 23, p = 0.49). The pre-operative KS Knee Score (KS-KS) was significantly lower in the PS group (PS: 44 ± 14 vs. MC-PLR: 53 ± 18, p < 0.05). At 12-months post-operation, there was significant improvement in all parameters (p < 0.01). Both groups had similar ROM (PS: 115º ± 13º vs. MC-PCLR: 114º ± 10º, p = 0.98), OKS (PS: 41 ± 5 vs. MC-PCLR: 40 ± 4, p = 0.50), KS-FS (PS: 74 ± 22 vs. MC-PCLR: 77 ± 16, p = 0.78), and KS-KS (PS: 89 ± 10 vs. MC-PCLR: 89 ± 10, p = 0.89). The PS group had significant improvement in all parameters from preoperation to 3-month postoperation (p < 0.05), but not from 3-month to 1-year postoperation (p ≥ 0.05). The MC-PCLR group continued to have significant improvement from 3-month to 1-year postoperation (p < 0.05). Preserving the PCL when using MC may paradoxically cause an undesired additional restrain that slows the recovery process of the patients after TKA. Compared to MC-PCLR, a PS TKA may expect significantly faster improvement at 3 months post operation, although they will achieve similar outcomes at 1-year post operation.

PCL retained is safe in medial pivot TKA-a prospective randomized trial

PURPOSE

Medial pivot (MP) designs resemble native knee kinematics and restore the "natural" kinematics of a knee after total knee arthroplasty (TKA). However, whether to preserve or resect the posterior cruciate ligament (PCL) is still under debate. We inquired whether sacrificing the PCL would improve range of motion, functional outcomes, and limb alignment compared to preserving the PCL in TKA using medial pivot implants (MP-TKA).

METHODS

This prospective, double-blinded, randomized controlled trial consisted of 33 patients (66 knees) undergoing bilateral simultaneous MP-TKA. In one knee, a PCL preservation technique was performed, and in the contralateral knee, the PCL was resected. The primary outcome was postoperative range of motion (ROM). The secondary outcomes were visual analogue scale (VAS) score for knee pain at walking, Knee Injury and Osteoarthritis Outcome Score for symptoms (KOOS-S) and quality of life (KOOS-QoL), Oxford knee score (OKS), and Forgotten Joint Score (FJS), and measurement of the mechanical femoral-tibial axis (mFTA) on X-ray images. All patients were followed up for a minimum of 2 years after surgery.

RESULTS

Patients who underwent MP-TKA with PCL preservation had a similar ROM at 2 years (125.45 ± 7.00 vs. 126.21 ± 6.73, p = 0.65) as those who underwent MP-TKAs with PCL resection. There was also no difference in VAS score (1.94 ± 0.79 vs. 2.00 ± 0.71, respectively, p = 0.51), OKS (39.97 ± 2.01 vs. 39.67 ± 2.03, respectively, p = 0.52), KOOS-S (84.41 ± 3.77 vs. 84.19 ± 3.57, respectively, p = 0.92), KOOS-QoL (82.94 ± 4.76 vs. 82.75 ± 4.70, respectively, p = 0.84), or FJS (72.66 ± 8.99 vs. 72.35 ± 8.64, respectively, p = 0.76) at the 2-year follow-up. No difference in the measurement of the mFTA was found between the two groups (180.27 ± 2.25 vs. 181.30 ± 2.13, respectively, p = 0.59).

CONCLUSION

This study demonstrated that both medial pivot TKA with PCL preservation and PCL resection achieved excellent results. There was no difference at the 2-year follow-up in terms of postoperative ROM, patient-reported outcomes, or radiographic evaluation.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Complications and Implant Survival of Total Knee Arthroplasty in People with Hemophilia

Total knee arthroplasty (TKA) is a commonly used option in advanced stages of knee arthropathy in people with hemophilia (PWH). The objective of this article is to determine what the complication rates and implant survival rates in PWH are in the literature. A literature search was carried out in PubMed (MEDLINE), Cochrane Library, Web of Science, Embase and Google Scholar utilizing the keywords "hemophilia TKA complications" on 20 October 2022. It was found that the rate of complications after TKA in PWH is high (range 7% to 30%), although it has improved during the last two decades, possibly due to better perioperative hematologic treatment. However, prosthetic survival at 10 years has not changed substantially, being in the last 30 years approximately 80% to 90% taking as endpoint the revision for any reason. Survival at 20 years taking as endpoint the revision for any reason is 60%. It is possible that with a precise perioperative control of hemostasis in PWH, the percentage of complications after TKA can be diminished.