Magnetic resonance imaging analysis of the bioabsorbable Milagro™ interference screw for graft fixation in anterior cruciate ligament reconstruction

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months

Is tibial tuberosity-trochlear groove distance an appropriate measure for the identification of knees with patellar instability?

PURPOSE - Tibial tuberosity-trochlear groove distance (TT-TG) has been regarded as a useful tool for establishing therapeutic choices for patellar instability. Recently, it has been shown that TT-TG negatively correlated with the quadriceps angle, suggesting that if used individually, neither provide a valid measure of instability. This study aimed to compare TT-TG distance between both knees in patients with unilateral instability to assess whether this measurement is a decisive element in the management decisions for patellar instability. METHODS - Sixty-two patients (18 male and 44 female), reporting to a specialist patella clinic for recurrent unilateral patellar instability, were included in the study. Patients underwent bilateral long leg computed tomography scan to determine TT-TG distance in both knees. Tibial TT-TG in symptomatic and asymptomatic knees in the same individual was compared statistically. RESULTS - Mean TT-TG distance in the symptomatic knee was 16.9 (±4.9) mm, compared to 15.6 (±5.6) mm in the asymptomatic knee. Tibial TT-TG was not significantly different between stable and unstable knees (n.s.). CONCLUSIONS - The lack of difference in TT-TG distance between stable and unstable knees suggests that TT-TG distance alone may not be a decisive element in establishing therapeutic choices for patellar instability. It should, therefore, be interpreted with caution during clinical evaluations. LEVEL OF EVIDENCE: II

Is tibial tuberosity-trochlear groove distance an appropriate measure for the identification of knees with patellar instability?

PURPOSE - Tibial tuberosity-trochlear groove distance (TT-TG) has been regarded as a useful tool for establishing therapeutic choices for patellar instability. Recently, it has been shown that TT-TG negatively correlated with the quadriceps angle, suggesting that if used individually, neither provide a valid measure of instability. This study aimed to compare TT-TG distance between both knees in patients with unilateral instability to assess whether this measurement is a decisive element in the management decisions for patellar instability. METHODS - Sixty-two patients (18 male and 44 female), reporting to a specialist patella clinic for recurrent unilateral patellar instability, were included in the study. Patients underwent bilateral long leg computed tomography scan to determine TT-TG distance in both knees. Tibial TT-TG in symptomatic and asymptomatic knees in the same individual was compared statistically. RESULTS - Mean TT-TG distance in the symptomatic knee was 16.9 (±4.9) mm, compared to 15.6 (±5.6) mm in the asymptomatic knee. Tibial TT-TG was not significantly different between stable and unstable knees (n.s.). CONCLUSIONS - The lack of difference in TT-TG distance between stable and unstable knees suggests that TT-TG distance alone may not be a decisive element in establishing therapeutic choices for patellar instability. It should, therefore, be interpreted with caution during clinical evaluations. LEVEL OF EVIDENCE: II

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

PURPOSE: Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images. METHODS: Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions. RESULTS: Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87-0.88; p < 0.001). CONCLUSIONS: The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited. LEVEL OF EVIDENCE: Development of diagnostic criteria in a consecutive series of patients and a universally applied 'gold' standard, Level II

The trochlear isometric point is different in patients with recurrent patellar instability compared to controls: a radiographical study

Purpose: The purpose of the study was to investigate the theoretical isometric point based of the curve of the femoral groove and relating it to the origin of the MPFL femoral tunnel on lateral radiograph by comparing a patellar instability cohort with a control cohort. Methods: From a Patellar Instability database the radiographs of 40 consecutive patients were analysed to define Schöttle’s point, and the arc of the circle of the trochlear groove. A comparison population of 20 radiographs from comparable patients with tibiofemoral joint disorders was used as a control. The distance from Schöttle’s point to the most anterior part of the groove (extension) was also compared to the distance to the distal end of the roof of the notch (flexion). Results: The trochlea was circular in the controls but not the Patellofemoral Instability cohort where trochlear dysplasia is usually present. The difference between the extension and flexion length was a mean of − 2.0 ± 0.5 mm in the controls and + 6.0 ± 0.5 mm in the patellofemoral cohort. In neither cohort did the centre of the circle correspond to Schöttle’s point. The extension distance correlated with the boss height. Conclusions: The dysplastic trochlea is not circular and the centre of the best matched circle was different to the control trochleae which were circular. The circle centres did not correlate with Schöttle’s point for either cohort, and was more proximal in the Patellofemoral Instability cohort. Clinical relevance: For the MPFL to have equal tension throughout flexion within the groove, the length should not change. In normal knees the MPFL does not behave isometrically. The change in length, as measured from Schöttle’s point to the trochlea, was greater for patellofemoral instability patients explaining why an isolated MPFL reconstruction in the presence of severe trochlear dysplasia risks poor outcomes

Non-Anatomic Proximal Realignment for Recurrent Patellar Dislocation Does Not Sufficiently Prevent Redislocation

Several operative techniques have been described for recurrent patellar dislocation. Clinical results vary depending on the procedure and indication. The present study aimed to evaluate the clinical outcome of Insall’s proximal realignment for recurrent patellar dislocation at mid-term follow-up. Forty-five patients were reviewed with a mean follow-up period of 49 months after having undergone Insall’s procedure. Outcome measures included reports of redislocations, complications, patient-reported outcome scores (Kujala, Tegner activity scale) and subjective assessment. No statistically significant improvements (p < 0.05) in patient-reported outcome measures were noted. Sixteen patients (35%) had poor to fair results using the Kujala score. Subjective assessment revealed that 12 patients (27%) were dissatisfied with the outcome of their surgery and would not undergo the same procedure. Ten patients (22%) had suffered from redislocation at the latest follow-up. In 4 cases (9%), intra-articular knee hematoma occurred which required arthroscopic intervention. The overall mid-term outcome of the present study shows low patient satisfaction. Non-anatomic realignment for recurrent patellar dislocation does not adequately prevent redislocation

Origin and insertion of the medial patellofemoral ligament: a systematic review of anatomy.

PURPOSE: The medial patellofemoral ligament (MPFL) is the major medial soft-tissue stabiliser of the patella, originating from the medial femoral condyle and inserting onto the medial patella. The exact position reported in the literature varies. Understanding the true anatomical origin and insertion of the MPFL is critical to successful reconstruction. The purpose of this systematic review was to determine these locations. METHODS: A systematic search of published (AMED, CINAHL, MEDLINE, EMBASE, PubMed and Cochrane Library) and unpublished literature databases was conducted from their inception to the 3 February 2016. All papers investigating the anatomy of the MPFL were eligible. Methodological quality was assessed using a modified CASP tool. A narrative analysis approach was adopted to synthesise the findings. RESULTS: After screening and review of 2045 papers, a total of 67 studies investigating the relevant anatomy were included. From this, the origin appears to be from an area rather than (as previously reported) a single point on the medial femoral condyle. The weighted average length was 56 mm with an 'hourglass' shape, fanning out at both ligament ends. CONCLUSION: The MPFL is an hourglass-shaped structure running from a triangular space between the adductor tubercle, medial femoral epicondyle and gastrocnemius tubercle and inserts onto the superomedial aspect of the patella. Awareness of anatomy is critical for assessment, anatomical repair and successful surgical patellar stabilisation. LEVEL OF EVIDENCE: Systematic review of anatomical dissections and imaging studies, Level IV