In vivo study of a new TKA design using dynamic RSA model

Scopo: Valutare, utilizzando il modello d’analisi radiostereometrica dinamica (RSA), il comportamento biomeccanico della Protesi Totale di Ginocchio (TKA) di nuovo design Stabilizzata Posteriormente (PS) a piatto fisso (FB) in vivo mentre i pazienti eseguono due compiti motori. L’ipotesi era che il modello d’analisi RSA dinamica fosse in grado di rilevare comportamenti diversi della protesi in condizioni di carico e di non-carico. Materiale e Metodi: Una coorte di 15 pazienti non consecutivi è stata valutata mediante RSA dinamica a 9 mesi dall’impianto di TKA. L’età media dei pazienti era 73,4 (65 – 72) anni. Le valutazioni cinematiche sono state eseguite utilizzando un dispositivo RSA (BI-STAND DRX 2) sviluppato nel nostro istituto. Ai pazienti è stato chiesto di eseguire 2 attività motorie attive: alzata dalla sedia in condizione di carico; Range di Movimento (ROM) stando seduti sulla sedia. I parametri di movimento sono stati valutati utilizzando la decomposizione di Grood e Suntay e i metodi di cinematica low-point. Risultati: La valutazione RSA dinamica ha mostrato una differenza significativa (p<0,05) tra il comportamento biomeccanico della protesi durante i 2 compiti motori. Se sottoposto al peso del paziente (nell’alzata da seduto), il low point del compartimento mediale ha un movimento più corto (5,7 ± 0,2 mm) rispetto al compartimento laterale (11,0 ± 0,2 mm). Questo realizza un movimento di pivot mediale come nel ginocchio normale. Durante il ROM, dove il paziente non carica sulla protesi, questa differenza non era invece presente: il compartimento mediale aveva uno spostamento di 12,7 ±0,2 mm, mentre il laterale aveva 17,3 ± 0,2 mm. Conclusioni: Il modello basato sulla RSA si è dimostrato uno strumento efficace per la valutazione della biomeccanica della TKA. Mediante l’uso sistematico di questo protocollo di studio, potrebbero essere effettuati futuri confronti fra diversi impianti, contribuendo in modo significativo al miglioramento del design della TKA.Aim: To evaluate in vivo using the RSA model of the biomechanical behaviour of new posteriorly stabilized (PS), fixed bearing (FB) total knee arthroplasty (TKA) while patients complete common motor tasks. The hypothesis was that dynamic RSA model was able to detect different behaviours of the implant with or without load. Materials and methods: A sample of 15, non consecutive patients has been evaluated using dynamic RSA for 9 months from the implantation of TKA. Mean age of the patiens was 73,4 (65 – 72) years old. Kinematic evaluations have been performed with a RSA tool (BI-STAND DRX 2) developed at IOR. Patients were asked to perform 2 different motor activities: sit to stand in weight bearing condition; ROM while seating on the chair. Movement parametess have been evaluated using Grood and Suntay decomposition and low point kinematics. Results: The evaluation with dynamic RSA showed a statistically significant difference (p<0,05) between the behaviour of the implant during the two motor tasks. Under weight bearing condition (sit to stand), low point of the medial compartment has a shorter movement (5,7 ± 0,2 mm) compared to lateral compartment (11,0 ± 0,2 mm). This is doing a medial pivotal movement as a normal knee. During ROM task, in an unloading condition, this difference was not present: medial compartment had a shift of 12,7 ±0,2 mm, while lateral had 17,3 ± 0,2 mm. Conclusion: RSA based model proved to be a working tool to evaluate biomechanics in TKA. With a systematic use of this study protocol, future comparisons between different implants could be done

Deep-dished highly congruent tibial insert in CR-TKA does not prevent patellar tendon angle increase and patellar anterior translation

PURPOSE: Starting from the hypothesis that a deep-dished highly congruent tibial insert in cruciate-retaining total knee arthroplasty would prevent the increase in patellar tendon angle and anterior patellar translation by reducing the paradoxical anterior femoral translation, the main purpose of the present study was to investigate the effect of this prosthesis design, and secondary to assess the clinical outcomes at 6-month follow-up. METHODS: Twenty patients treated with cruciate-retaining total knee arthroplasty with navigation technique were enrolled and prospectively followed up at 6 months. The median value of age was 71 years (57-83). Before and after surgery, the following parameters were calculated: patellar tendon angle, anterior-posterior and medio-lateral patellar translation, patellar height and range of motion. All patients were assessed with the SF-36 Physical Functioning and the Knee injury and Osteoarthritis Outcome Score ADL scores. RESULTS: Patellar tendon angle and anterior patellar translation significantly increased in post-operative conditions (p < 0.0001); a statistically significant medial patellar translation was found (p < 0.0001), while patellar height did not show any difference between pre- and post-operative conditions (n.s). A significant correlation was found between patellar tendon angle and anterior patellar translation and the clinical scores (p < 0.0417). There was a significant post-operative decrease (p < 0.0033) in the range of motion. CONCLUSIONS: The present study failed to demonstrate that deep-dished highly congruent tibial insert prevents the anterior translation of the patella in cruciate-retaining total knee arthroplasty, thus causing inferior clinical scores. It provided useful information about the biomechanical role of the patella in total knee arthroplasty, allowing to choose the most appropriate surgical approach. LEVEL OF EVIDENCE: Case series, Level IV

Roentgen stereophotogrammetric analysis: an effective tool to predict implant survival after an all-poly unicompartmental knee arthroplasty\u2014a 10\ua0year follow-up study

The main purpose of the present study was to determine long-term implant fixation of 15 unicompartmental knee arthroplasty (UKAs) with an all-poly tibial component using Roentgen stereophotogrammetric analysis (RSA) at a mean 10-year follow-up. The secondary purpose was to investigate whether the progressive loss of implant's fixation correlates with a reduction in Knee society score (KSS). METHODS: Fifteen non-consecutive patients with primary knee osteoarthritis received a UKA with an all-poly tibial component were assessed using KSS scores pre-operatively and post-operatively and RSA on day 2 after surgery, then at 3, 6, and 12 months and yearly thereafter. The mean last follow-up was 10 years. RESULTS: An increase in maximum total point motion (MTPM) values from 6 months to 1 year post-operatively was found respect to post-operative reference. Implants' displacement values were always 0.2 mm in revised UKAs. A linear and negative correlation with statistical significance was found between MTPM and both clinical and functional KSS scores (p < 0.001). CONCLUSION: Also in a long-term follow-up evaluation, RSA is an effective tool to predict functional results after an all-poly UKA providing also a relevant predictive value at 1 year follow-up, and this can be very useful for both patients and surgeons

Soft Tissue balancing of the knee flexion

Soft Tissue Balancing in Primary Total Knee Arthroplasty is proposed as a practical text for the man- agement of soft tissue balancing, presenting step-by-step descriptions of surgical technique. The text was intended to be a pragmatic reference for students, residents, fellows and attending surgeons engaged in the treatment of patients who have undergone knee replacement surgery. This book uses \u201chow to\u201d approach for many of the complex issues confronting us in total knee arthroplasty, written by some expert authors. It is devoted to issues relating to primary total knee arthroplasty \u2013 from simple to the most complex. The first and second chapters include the primary technique in knee arthroplasty outlining tips and pearls dur- ing the surgical procedure. Some of the chapters emphasize principles of primary in cruciate retaining and posterior stabilized implants underlining the differences in soft tissue balancing and showing the use of navigation system. The last chapters show \u201chow to\u201d perform the soft tissue balancing in different deformi- ties, such as varus and valgus, flexed and stiff knees. Last, but not least, the final chapter draws attention in extensor mechanism issues. We feel glad to have received the support of so many well-know master surgeons who have contributed to the text. We are grateful to all of them and are proud to have been able to present their combined ex- perience in the proceeding book. It is a true honour for us to have collaborated with outstanding friends, colleagues and mentors in publishing this textbook. As editors, we have each learned a great deal from the authors who have contributed to this text. We expect that their efforts will be equally valuable to you

Good survivorship of all-polyethylene tibial component UKA at long-term follow-up

Purposes: To determine the long-term survival rate of an all-polyethylene tibial unicompartmental knee arthroplasty (UKA) in a large series of consecutive patients and to investigate the possible factors that could influence the outcome. Methods: A retrospective evaluation of 273 patients at 6\u201313\ua0years of follow-up was performed. Clinical evaluation was based on KSS and WOMAC scores. Subjective evaluation was based on a visual analogue scale for pain self-assessment. Radiographic evaluation was performed to assess femoral-tibial angle (FTA), posterior tibial slope (PTS) and tibial plateau angle (TPA). A Kaplan\u2013Meier survival analysis was performed assuming revision for any reason as primary endpoint. Results: The 10-year implant survivorship was 87.6\ua0%. Twenty-five revisions (9.2\ua0%) were performed, and aseptic loosening of the tibial component was the most common failure mode (11 cases, 4\ua0%). The comparison of survival rate according to age at surgery did not show significant difference. Age at surgery, FTA, TPA and PTS were not related to higher risk of revision. No correlations were found between BMI, age at surgery and clinical scores. Finally, no statistical differences of radiographic measurements were found between revisions and non-revisions. Conclusions: The present study has demonstrated on a large series of patients that UKA with an all-polyethylene tibial component, with an accurate technique and a proper patient selection, can provide a satisfactory clinical and functional outcome and a good overall survivorship of the implant at long-term follow-up. These advantages could be achieved at a lower cost. Level of evidence: Retrospective Therapeutic Study, Level IV

Arthroscopic-assisted focal resurfacing of the knee with minimal bone resection: Surgical technique and preliminary clinical results

The main purpose of this paper is to describe a new arthroscopic-assisted surgical technique for focal resurfacing of the medial tibiofemoral compartment. The secondary aim is to present the preliminary clinical and radiographic results in a case series of 13 consecutive patients at a mean follow-up of 29 months. All patients were treated with the presented surgical procedure between November 2006 and March 2007 for Ahlback grade 3 osteoarthritis restricted to the medial tibiofemoral compartment. Subjective evaluation was based on a visual analogue scale for self-assessment of joint pain. Objective clinical evaluation was based on the Hospital for Special Surgery score. Range of motion was evaluated with a manual goniometer. Radiographic evaluation compared hip-knee-ankle angle preoperatively and postoperatively. The presented technique has shown good clinical and functional results. The Hospital for Special Surgery score and visual analogue scale showed a significant improvement (P<0.0001 and P=0.0002, respectively). Range of motion and axial alignment were not significantly modified with respect to preoperative condition. Despite the small sample size and short follow-up, an arthroscopic-assisted procedure for focal resurfacing of the medial compartment of the knee can be a viable option for early-onset osteoarthritis in selected cases, providing good pain relief and functional results at 2-year follow-up

Unicompartmental knee arthroplasty in patients over 75\ua0years: a definitive solution?

The purpose of this study was to perform a mid-long-term clinical and radiographic evaluation of the results obtained in patients older than 75\ua0years treated with minimally invasive unicompartmental knee arthroplasty (UKA). The hypothesis was that UKA is a viable solution for the definitive treatment of localized disease in this age group, with good results and a low failure rate

The adductor tubercle: an important landmark to determine the joint line level in revision total knee arthroplasty

Purpose The restoration of the physiological femoro-tibial joint line (JL) is important to obtain a good outcome in revision total knee arthroplasty (RTKA). However, its assessment is challenging. The ratio of the distance between the adductor tubercle (AT) JL (ATJL) and the trans-epicondylar femoral width (FW) was proposed as a reliable method. The purpose of this study was to check whether this ratio is a reliable tool to restore the prosthetic JL height in challenging prosthetic revision cases. Methods Twenty-one patients (mean age 65.8 years) were recruited. During surgery, FW was measured and ATJL distance was calculated using 0.53 (SD 0.03) as the ratio. After implant positioning, the obtained ATJL line was measured to verify the accuracy of the surgical procedure. Thirteen patients presented a healthy contralateral knee: a comparative radiograph examination was performed to verify the appropriateness of the restored JL height. Results The intra-operatively calculated ATJL was not significantly different with respect to the measured ATJL obtained after prosthetic component implantation. The comparative analysis between the restored JL and the JL of the contralateral not operated knee was also not statistically significant, thus confirming the appropriateness of the restored JL height. Conclusions This study shows that the method which uses an AT to JL distance/FW ratio to determine the JL level, previously applied in primary TKA, is valid when using intra-operatively acquired measurements in RTKA. This is clinically relevant since it represents a reliable tool which helps surgeons to restore the JL level in challenging prosthetic revision cases