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INTRODUCTION: In revision total hip arthroplasty (THA), the advent of porous custom-made triflange acetabular implants with 3D scan planning offers a new perspective to improve implantation accuracy and anatomical restoration of the center of rotation (COR). This issue was investigated using CT-scan as the measurement tool, but in limited series (±10 cases) and without investigating the factors that may influence errors in positioning. Therefore we performed a retrospective study aiming to: (1) assess the placement accuracy of such implants with respect to the preoperative planning, (2) examine whether the volume of bone to be resected in order to apply the implant had an impact on this accuracy, (3) assess if errors in position at surgery had any influence on function, complications and survival. HYPOTHESIS: Preoperative planning could be accurately reproduced when implanting porous custom-made acetabular implants, and that accuracy would decrease in proportion to the volume of bone to be resected METHOD: Twenty patients undergoing THA revision with porous custom-made acetabular implants were included in this single-center retrospective study. Mean follow-up was 17.9 months ± 9.4 [2-45.1]. Preoperative planning was performed using 3D scanographic modeling. A post-operative CT scan was performed to assess implantation accuracy in terms of orientation and COR restitution. Demographic data, Oxford scores, complications and survival were recorded. RESULTS: Mean deviation from the preoperative planning in inclination, anteversion and rotation were 4.3 ° ± 2.5, 6.1 ° ± 4.7, and 7 ° ± 4.6, respectively. Restoration of the COR showed a mean deviation of 2.1 ± 1.3 mm anteroposteriorly, 2.5 ± 2 mm mediolaterally and 2.2 ± 1.3 mm proximodistally. In total, 45% (9/20) of implants were positioned with perfect restoration of orientation (±10 °) and COR (±5 mm). The mean planned bone resection was 8.1 ± 4.9 cm3, with placement accuracy and COR restitution decreasing significantly when the volume of bone to be resected exceeded 2.7 cm3. One dislocation was found (5%, 1/20). Survival at last follow-up was 100%, the mean Oxford score at follow-up was 31.7 ± 7.9 [16-52], without being influenced by errors in position or COR restitution. CONCLUSION: In total 45% of the implants restored an orientation and a COR as planned, particularly when the volume of bone to be resected is less than 2.7 cm3. Although these are complex cases with large amounts of bone loss, 3D manufacturing could give us hope of greater precision. The link between better precision and low bone resection volume could be an area to develop with the manufacturer in order to improve results. LEVEL OF EVIDENCE: III; diagnostic using CT in transversal retrospective study.
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BACKGROUND: Several Medial Patellofemoral Ligament (MPFL) reconstruction techniques have been developed, and those with soft tissue fixation are often preferred in children because they allow the growth cartilage to be preserved. Nevertheless, the recurrence rate of patellar dislocation varies widely from one series to another, with no clear superiority of one technique in the pediatric setting. The objectives of this study were to compare the results of two tendon graft fixation techniques (tendon-tendon fixation and anchor-screw fixation) by analyzing: 1) the rate of patellar dislocation recurrence, 2) clinical outcomes, 3) tourniquet time and 4) complication rate. HYPOTHESIS: The two tendon graft fixation techniques used in MPFL reconstruction are equivalent in terms of the patellar dislocation recurrence rate. PATIENTS AND METHODS: This is a retrospective comparative study including 57 patients with a median age of 14 years (12-15 years) who underwent MPFL reconstruction between 2016 and 2020. The tendon graft was fixed upon itself, after passing through a patellar tunnel (Group A: tendon-tendon fixation; n=29) or by two anchors and an interference screw (Group B: anchor-screw fixation; n=28). The preoperative radiographic data were comparable in the two groups: patellar height [A: 1.3 (interquartile range (IQR): 1.2-1.4) / B: 1.2 (IQR: 1-1.4) (p=0.21)], tibial tuberosity to trochlear groove (TTTG) distance [A: 16 (IQR: 13-19) / B: 13.5 (IQR: 11.5-18.8) (p=0.12)], patellar tilt [A: 25 (IQR: 20-35) / B: 24.5 (IQR: 21-32) (p=0.93)]. For each technique, the rate of patellar dislocation recurrence, clinical and functional results (Kujala score, Marx activity score, Lille patellofemoral score), complications (pain, stiffness, revision) were analyzed. In addition to MPFL repair, 13 patients (2 in Group A, 11 in Group B) underwent additional orthopedic procedures to enhance patellar stability. RESULTS: no patients were lost to follow-up and the median follow-up was 30 months (IQR: 20-38). The dislocation recurrence rate was higher in Group A, 6.9% (2/29) compared to none in Group B. The clinical results were comparable for the two groups with a Kujala score [A: 94 (IQR: 89-100) / B: 92 (IQR: 87.5-94.5) (p=0.12)]; Marx score [A: 10 (IQR: 7-11) / B: 9.5 (IQR: 7.5-12) (p=0.89)] and Lille patellofemoral score [A: 97 (IQR: 91-100) / B: 94 (IQR: 90-98) (p=0.21)]. The tourniquet time was shorter in Group A than in Group B, 61minutes (IQR: 52-71) versus 85minutes (IQR: 55-115) (p=0.024) excluding additional orthopedic procedures. The complication rate was 17.2% (5/29) in Group A (dislocation n=2, stiffness n=2, ATT (anterior tibial tuberosity) revision with screw removal n=1) and 10.7% (3/28) in B (pain n=1, ATT revision with screw removal n=2) (p=0.35). CONCLUSION: Clinically, anchor-screw fixation appears to reduce the risk of patellar dislocation recurrence but this could not be statistically tested. On the other hand, the two techniques are comparable in terms of the functional results. LEVEL OF EVIDENCE: III; retrospective case-control study.