Comparing the accuracy of high tibial osteotomies between computer navigation and conventional methods.

BACKGROUND: The accuracy of correction has been shown to be an important determinant in long-term outcomes of patients who were treated with a medial open-wedge high tibial osteotomy (HTO) who suffer from unicompartmental osteoarthritis (OA). Computer navigation systems have the potential to improve surgical precision. The purpose of this study was to compare radiographic outcomes between patients treated with a navigation system and those treated through conventional methods of assessing alignment intra-operatively. The null hypothesis was that the method of assessing the alignment intra-operatively would make no difference in the accuracy of correction. METHODS: In this retrospective study, 107 patients with medial varus OA who were managed by open-wedge HTO were included. Of the 107 patients, 41 were treated using an intraoperative navigation system and 66 were treated using conventional methods. Pre-operative and post-operative single-leg, long-leg standing alignment films were used to determine the extent of pre-operative varus deformity and the post-surgical correction achieved compared to the predetermined target range. RESULTS: The navigational system had eight instances of software malfunction (19.5%) intra-operatively and correction was determined using the cable method. These results were analyzed as part of the conventional group. Post-operative radiographic differences were significant between the two groups. In the navigation group, 75.8% of the patients were corrected within the target range compared to 66.2% in the conventional group. More patients were also under corrected (to the point of remaining in varus) using conventional methods compared to a navigation system. There was no statistically significant difference in the degree of correction in the sagittal plane between the two groups. Regardless of the method used for checking alignment intra-operatively, there was a statistically significant difference in post-operative weight-bearing measurements when the surgeon had intra-operative axial loading versus when they did not. CONCLUSION: For coronal plane corrections, the navigation system was shown to have greater success in achieving the desired correction value and in having fewer patients who were under corrected. Despite the measurement technique a surgeon chooses to assess the accuracy of correction, axial loading the extremity in order to simulate the weight-bearing film alignment post-operatively is important to maximize the accuracy of correction needed.

Clinical Accuracy of J-Sign Measurement Compared to Magnetic Resonance Imaging.

BACKGROUND: The J-sign is defined as lateral patellar translation over the anterolateral femur proximal to the trochlear groove during active leg extension. Dynamic magnetic resonance imaging (MRI) techniques allow for quantification of the J-sign using a variety of published indices. However, to date, clinical quantification of the J-sign has not been reliably described. The purpose of the present study is to assess the accuracy of clinically quantifying the J-sign compared with objective MRI data. METHODS: All patients in this case series were indicated for Fulkerson osteotomy due to recurrent lateral patellar instability and examined preoperatively for the presence of J-sign. The J-sign was estimated by placing a finger on the lateral edge of the trochlea and estimating the lateral translation of the patella while the patient actively extended the knee from 30 degrees of flexion to maximum extension. Independent preoperative measurements were obtained by both the senior author and a resident and compared to dynamic MRI measurements read by independent investigators. RESULTS: Preoperative physical examination for the presence of the J-sign was conducted on 10 patients (10 knees). The average difference between clinical and MRI J-sign measurement was 4.32 mm (range 0.2 - 10.4 mm). There was no significant difference between the clinical and MRI J-sign measurements (p = 0.2579). Clinical measurements of the J-sign differed by an average of 2.2 mm between the two examiners (range 0 - 5 mm). CONCLUSIONS: Clinical quantification of the Jsign showed relative imprecision when compared with MRI measurements of the modified lateral patellar edge (LPE), though in several patients we did achieve accurate J-sign assessment. If further research can validate this technique as accurate and consistent using larger patient populations, it could aid in the development of surgical treatment plans for patients presenting with patellar instability, and serve as an objective assessment of alignment in the postoperative period.

Lateral patellofemoral ligament reconstruction to restore functional capacity in patients previously undergoing lateral retinacular release.

AIM: To study patient outcomes after surgical correction for iatrogenic patellar instability. METHODS: This retrospective study looked at 17 patients (19 knees) suffering from disabling medial patellar instability following lateral release surgery. All patients underwent lateral patellofemoral ligament (LPFL) reconstruction by a single surgeon. Assessments in all 19 cases included functional outcome scores, range of motion, and assessment for the presence of apprehension sign of the patella to determine if LPFL reconstruction surgery was successful at restoring patellofemoral stability. RESULTS: No patients reported any residual postoperative symptoms of patellar instability. Also no patients demonstrated medial patellar apprehension or examiner induced subluxation with the medial instability test described earlier following LPFL reconstruction. Furthermore, all patients recovered normal range of motion compared to the contralateral limb. For patients with pre and postoperative outcome scores, the mean overall knee injury and osteoarthritis outcome score increased significantly, from 34.39 preoperatively (range: 7.7-70.12) to 69.54 postoperatively (range: 26.82-91.46) at final follow-up (P < 0.0001). CONCLUSION: This novel technique for LPFL reconstruction is effective at restoring lateral restraint of the patellofemoral joint and improving joint functionality.