Bertrand Boyer

The role of the medial ligamentous structures on patellar tracking during knee flexion

PurposeThe influence of the medial patellar ligamentous structures on patellar tracking has rarely been studied. Thus the main purpose of this cadaveric biomechanical study was to determine the influence of the medial patellofemoral (MPFL), medial patellomeniscal (MPML) and medial patellotibial (MPTL) ligaments on the three-dimensional patellar tracking during knee flexion. This study was conducted using a validated cadaveric optoelectronic protocol for analysis of patellar kinematics.MethodsFor each cadaveric knee study, four successive acquisitions were performed; first was studied patellar tracking in healthy knees, then the junction between MPFL and vastus medialis obliquus (VMO) was sectioned, the MPFL was released at its patellar attachment and finally was released the insertion of the MPML and MPTL.ResultsIn this study, the MPFL accounts for 50–60% of the medial stabilization forces of the lateral patellar shift during patellar engagement in the femoral trochlea. This work confirm and clarify the role of the MPFL as the primary stabilizer of the patella during the initial 30° of knee flexion. Moreover, this study shows no significant results regarding the stabilizing action of the VMO on the patella during knee flexion.ConclusionThis in vitro study, conducted with an experimental protocol previously validated in the literature, helps quantify the actions of the MPFL, the VMO, and the MPML/MPTL respectively, and identify areas of joint motion where these structures have the most significant influence. This confirms the importance of reconstruction in the treatment of chronic patellar instability. During its reconstruction, care should be taken to adjust the MPFL balance during the initial 20°–30° of flexion.

Survival of cementless dual mobility socket with a mean 17 years follow-up

PURPOSE OF THE STUDY As part of the 2006 symposium of the French Hip and Knee Society devoted to the dual mobility socket, we report a retrospective multicentric series of 438 first-intention total hip prostheses with a dual mobility socket at a mean 17 years follow-up. The purpose of our report was to ascertain the 15-year survival of this socket and analyze failures. MATERIAL AND METHODS The series included 438 primary replacements. This was a homogeneous multicentric series. The cementless sockets were 80 Novae-1 titanium Serf cups and 358 Novae-1 stainless steel Serf cups. All stems were inserted without cement: 185 Pf((R)) stainless steel screwed Serf stems, 228 PRO titanium screwed Serf stems, and 25 Corail stems. The mobile polyethylene insert was retaining. All of the heads were 22.2-mm chromium-cobalt heads. Degenerative hip disease was the main etiology and mean follow-up was 17 years (range, 12-20). Mean age at implantation was 54.8 years (range, 23-87). The actuarial method with a 95% confidence interval was used to determine the 15-year cup survival rate. RESULTS At the last follow-up, none of the patients had presented an episode of early or late instability. Analysis of the socket at last follow-up showed 13 aseptic loosenings, 23 intraprosthetic dislocations, and seven replacements of the polyethylene insert for wear. The overall 15-year prosthesis survival rate was 89.2+/-8.7%. The overall 15-year socket survival rate was 96.3+/-3.7%. DISCUSSION The fact that, at last follow-up, none of the implants had shown instability confirms the long-term stability of the dual mobility socket. The results in terms of 15-year survival confirm earlier reports. The main cause of failure was cup fixation, which is the weak point of this technique with the initial Novae cup design, which did not have hydroxyapatite coating. The second leading cause was intraprosthetic dislocation, which can be divided into three main categories. The first is intraprosthetic dislocation in a context of pure wear with normal function of the dual mobility socket; the retaining feature of the insert loses its efficacy due to wear. The second category is intraprosthetic dislocation in a context of cup loosening with a third-body effect and increased retention wear, in which case we consider that cup loosening is the primary event leading to rapid secondary wear and subsequent intraprosthetic dislocation. The third category is intraprosthetic dislocation caused by a blockage in a context of fibrosis or impingement involving severe heterotopic ossifications. We had only two femoral failures related to aseptic loosening, most certainly related to use of noncemented implants, which limits the extension of granulomas to the polyethylene. Studying the three series from Saint-Etienne more specifically, where three different configurations were used, it would appear that the titanium cup has a better survival rate and that the titanium used for the thinner necks may be an unfavorable factor for intraprosthetic dislocation.

Étude d'une série de 438 cupules non cimentées à double mobilité

PURPOSE OF THE STUDY Within the framework of the 2007 symposium of the French Hip and Knee Society devoted to the dual mobility socket, we report a retrospective multicentric series of 438 first-intention total hip prostheses with a dual mobile socket at 17 years mean follow-up. The purpose of our report was to ascertain the 15-year survival and analyze failures. MATERIAL AND METHODS The series included 438 first-intention prostheses. This was a homogeneous multicentric series. Sockets were: 80 Novae-1 titanium Serf cups and 358 Novae-1 stainless steel Serf cups. All stems were inserted without cement: 185 Pf) stainless steel screwed Serf stems, 228 PRO titanium screwed Serf stems, 25 Corail stems. The mobile polyethylene insert was retaining. All of the heads were 22.2mm chromium-cobalt heads. Degenerative hip disease was the main etiology and mean follow-up was 17.18 years (range: 12-20). Mean age at implantation was 54.8 years (range: 23-87). The actuarial method with 95% interval of confidence was used to determine the 15-year cup survival. RESULTS At last follow-up, none of the patients had presented an episode of early or late instability. Analysis of the socket at last follow-up showed: 13 aseptic loosenings, 23 intraprosthetic dislocations, and seven replacements of the polyethylene insert for wear. The overall 15-year prosthesis survival was 89.2+/-8.7%. The overall 15-year socket survival was 96.3+/-3.7%. DISCUSSION The fact that at last follow-up none of the implants had exhibited instability confirms the long-term stability of the dual mobility socket. The results in terms of 15-year survival confirm earlier reports. The main cause of failure was cup fixation, which is the weak point of this technique with the initial Novae cup, which did not have hydroxyapatite coating. The second leading cause was intraprosthetic dislocation, which can be divided into three main categories. The first is intraprosthetic dislocation in a context of pure wear with normal function of the dual mobility; the retaining feature of the insert looses its efficacy due to wear. The second category is intraprosthetic dislocation in a context of cup loosening with a third-body effect and increased retention wear, in which case we consider that the cup loosening is the primary event leading to secondary rapid wear and subsequent intraprosthetic dislocation. The third category is intraprosthetic dislocation cause by a cam effect in a context of fibrosis or impingement involving a large calcification. We have had only two femoral failures by aseptic loosening, most certainly related to use of noncemented implants, which limits the extension of granulomas to the polyethylene. Studying more specifically the three series from Saint-Etienne where three different configurations were used, it would appear that the titanium cup has a better survival and that the titanium used for the thinner necks would be an unfavorable factor for intraprosthetic dislocation.

Study of patellar kinematics after reconstruction of the medial patellofemoral ligament.

BACKGROUND Medial patellofemoral ligament reconstruction is currently the technique of choice for the treatment of patellar instability. But what should be the most appropriate graft tension for optimal restoration of patellofemoral kinematics? METHODS Six freshly frozen cadaveric knees were studied, the three bone segments were respectively equipped with opto-reflective markers. The acquisitions were made using the Motion Analysis System®. Six successive acquisitions were performed for each knee under different levels of graft tension. FINDINGS With an intact medial patellofemoral ligament, the medial patellar tilt increased up to a mean value of 2.02° (SD 3.1), the medial patellar translation gradually increased up to a mean value of 3.3mm (SD 2.25) with a slight lateral rotation over the first 30° of knee flexion with a maximum mean value of 1.22° (SD 0.8) at 20° of knee flexion. Reconstruction of the medial patellofemoral ligament was performed using different levels of tension applied to the graft. Only 10 N of graft tension could restore normal patellar tilt, lateral shift and rotation, with results approximating those measured on healthy knee. INTERPRETATION This study confirms the role of the medial patellofemoral ligament in providing adequate patellar stability during the first 30° of knee flexion. According to our findings, a 10 N tension applied to the graft appears sufficient to ensure proper control of patellar tracking whereas 20, 30 and 40 N of tension are excessive tension values inducing a major overcorrection in all studied parameters.

The anterolateral ligament: Anatomic implications for its reconstruction

BACKGROUND The purpose of this study was to define the best anatomic parameters with which to perform an accurate anterolateral ligament (ALL) reconstruction. These parameters were anatomical insertions, allowing favorable isometry, length variation during flexion, and anthropometric predictors of ALL lengths. METHODS A total of 84 fresh-frozen cadaver knees were dissected to analyze the ALL, focusing on its femoral insertion. The ALL length was measured in different degrees of flexion (extension, 30°, 60°, and 90° of flexion) and rotation (neutral, internal or external rotation). The ALL width and thickness were measured. A correlation between ALL length, the general knee size and individual characteristics was investigated. RESULTS The ALL was present in 80 specimens (95%). The femoral footprint was always posterior (5.52±0.93 mm, range 3.83-6.94) and slightly proximal (1.51±0.75mm, range 0.63-2.37) to the lateral femoral epicondyle. The mean ALL length increased with internal rotation and decreased with external rotation (P<0.05). The maximum ALL length was found at 30° of flexion, and the minimum at 90°. There was a significant correlation between the ALL length and height, sex, and proximal femur dimensions. CONCLUSION In order to get an anatomical reconstruction with favorable isometry, it is recommended that the ALL femoral graft is implanted posterior and slightly proximal to the epicondyle. It is also suggested that the tension be adjusted by fixing the graft between 0 and 30° of flexion, being tighter near extension. This will allow good rotational stability without implying any stiffness.

Wear analysis of hip explants, dual mobility concept: Comparison of quantitative and qualitative analyses

Total hip replacement fails mainly because of wear. It is of interest to analyse wear to be able to increase the longevity of the hip implants. One way to achieve it is to use instruments on explants but the most suitable depends on the application. This article aims at comparing several methods of surface analysis in the particular application of wear determination in a series of dual mobility explants. Wear measurement could help understand the wear mechanism only partially known. A coordinate measuring machine is used to get three-dimensional points representing the explants, then Pro/Engineer® and Matlab® are used to calculate wear. A mechanical (SOMICRONIC®) and an optical profilometer (Bruker nanoscope Wyko® NT 9100, ex. Veeco) are used to access roughness parameters. The comparisons of the two software showed similar results for wear calculation except in a few cases where differences are due to the theoretical volumes calculation. The comparison of the two profiling techniques resulted in similar results particularly for Sa and Sdr. The comparison of the results showed that wear is present for four explants; it is relevant with the observed characteristics. The mechanical profilometer showed better accuracy than the optical one which enable to conclude that it must not be neglected for that particular application, even if measurements need more time.

Correction to: Intraprosthetic dislocation of dual mobility total hip arthroplasty: still occurring?

The published online version contains mistake in the author list for the author name “Di Iorio Alexandre” was incorrectly presented.

Clinical And Radiological Predictors Of Medial Patellofemoral Ligament Reconstruction

Introduction: Among the numerous techniques available, medial patellofemoral ligament (MPFL) reconstruction is increasingly used for the surgical treatment of objective patellar instability. Although the value of this technique has been demonstrated, few studies have assessed predictors of good clinical results. The main objective of this study was to isolate, through a clinical series of 107 patients, the clinical and radiological predictors that can significantly influence the clinical results of the MPFL ligament. Methods: One hundred and seven patients (110 ligament reconstructions) presenting an objective patellar instability, were evaluated with a mean follow-up of 55 months (24 to 91). The standardized procedure comprised MPFL reconstruction using the gracilis tendon. Complementary distal bone graft was associated if a preoperative tibial tubercle-trochlear groove (TT-TG) distance exceeded 20 mm or a patella alta. Functional IKDC and Kujala scores were preoperatively assessed and at end of follow-up. Plain X-ray with radiological assessment of patellar height and tilt (Laurin angle, Merchant angle, Maldague classification) and a CT scan measurement of the patellar tilt (quadriceps contracted and relaxed) and TT-GT distance were performed preoperatively and at 6 months. Femoral tunnel position was assessed following the criteria formulated by Schöttle. The amount of femoral tunnel widening was measured by means of the 3D CT scan image at 6 months. Predictors were determined from univariate and multivariate analyzes integrating clinical and radiological criteria pre and postoperative. The variables of interest were defined as the difference in functional scores between pre and postoperative. Results: Clinical factors, such as age, Body Mass Index, number of dislocation, time between the first dislocation and surgery, did not influence functional scores (all p> 0.05). For technical factors: association with a bone graft or incorrect positioning of the femoral tunnel, also had no effect on clinical outcome (p> 0.05). It was the same for preoperative radiological factors: radiological and CT scan tilt, TT-TG distance, patellar height (all p> 0.05). For postoperative radiological factors, patellar height and tilt were not predictors. However, the correction of patellar tilt with quadriceps contracted (p = 0.013) and relaxed (p = 0.003) and the TT-GT distance correction (p = 0.023) were predictors of good clinical results. Discussion and Conclusion: For the MPFL ligament reconstruction, predictors of clinical improvement of the patient were patellar tilt and TT-GT distance correction at CT scan.

Study of a Titanium Dual-Mobility Socket with a Mean Follow-up of 18 Years

The concept of stainless steel dual-mobility cup in total hip arthroplasty has demonstrated a very low incidence of long-term instability and a 98% survival rate after 12 years. We systematically implanted titanium alloy dual-mobility acetabular cups during a 5-year period. The purpose of our retrospective study was to report the 18-year clinical results of a homogeneous and continuous series of 103 primary total hip replacements after implantation of a cementless titanium dual-mobility cup. The overall 18-year survival rate of the acetabular cup with a 95% confidence interval was 87.4%. At last follow-up, there was no evidence of implant instability. However, aseptic loosening of the acetabular component was reported in one case and high wear of the retentive liner in nine. The results of this investigation confirmed the long-term stability of dual-mobility implants. The main limitation of this system was early wear of the polyethylene liner in contact with the titanium metal back and third-body reaction associated with loss of the PE liner retentive rim. In our study, titanium demonstrated poor tribological characteristics.