D. T. T. Lie

The effects of lateral meniscal allograft transplantation techniques on tibio-femoral contact pressures

This paper reports a series of comparative tests in vitro, that examined how meniscectomy and meniscal allografting affected tibio-femoral joint contact pressure. Knees were loaded in axial compression and pressure maps obtained from the lateral compartment using Fuji Prescale film inserted below the meniscus. This was repeated after meniscectomy, and then after meniscal allografting with fixation by a bone plug for the insertional ligaments, plus sutures. Finally, the pressure, when the allograft was secured by sutures alone, was measured. The peak pressure rose significantly after meniscectomy, and then was reduced significantly by both allograft methods so that it was not significantly different to normal. Allografts fixed by sutures only allowed slightly higher contact pressure than when they had bone fixation. This study suggests that meniscal allografting should have a chondroprotective effect and that there is a small advantage from adding bony fixation to suture fixation.

Persistence of the mini pivot shift after anatomically placed anterior cruciate ligament reconstruction.

We hypothesized that traces of pivot-shift instability (a minipivot) would persist after anterior cruciate ligament reconstruction in some knees despite objective restoration of anteroposterior laxity to normal. We tested intact cadaver knees after anterior cruciate ligament transection and then after anatomically placed single-bundle anterior cruciate ligament reconstructions. We measured the rotational laxities and pivot-shift kinematics over a range of graft tensions. Increasing graft tension decreased anteroposterior laxity; anteroposterior laxity was greater than normal at 0 and 10 N tensions but not different than normal at 20 to 60 N tensions. Anterior cruciate ligament deficiency had little effect on rotation laxity, and reconstruction had little effect on rotational laxity, which was not reduced by increasing graft tension. During the pivot-shift test, increasing graft tension reduced the anteroposterior subluxation-reduction events, but tibial rotational was not restored to normal. More sophisticated reconstruction methods may be required to control rotation. Objective restoration of anteroposterior laxity to normal does not necessarily return knee kinematics, especially rotational behavior, to normal.

The Remains of Anterior Cruciate Ligament Graft Tension After Cyclic Knee Motion

Background There is sometimes a return of excess knee laxity after anterior cruciate ligament reconstruction. One of the contributing factors might be a loss in graft tension. It is unknown whether the tension imposed on an anterior cruciate ligament graft degrades with time and, if so, the effect of that loss of tension on knee laxity. Hypotheses The pretension in the anterior cruciate ligament graft reduces significantly within the first 500 motion cycles, and this decrease in graft tension causes an increase in knee laxity. Study Design Controlled laboratory study. Methods This study measured the remains of bone-patellar tendon-bone graft pretension after cyclical flexion-extension and the effect of any tension loss on knee laxity, using 8 cadaveric knees. A tension transducer was inserted into the graft and calibrated in situ. The reconstruction tension was 40 N at 20° of flexion. In test 1, the graft tension was measured under cyclical flexion-extension in a motorized rig up to 1500 cycles. Test 2, with a new graft, also included anteroposterior and internal-external rotational knee laxity measurements at 0, 500, and 1500 cycles. Results The graft tension at 0° of flexion dropped from 208 N, by 25% after 50 cycles, 41% by 500, and 46% by 1500 cycles. Anterior laxity increased from +1.4 to +2.8 mm by 500 cycles, and performing these laxity tests also caused significant tension losses. Clinical Relevance These results provide one possible explanation for early slackening of anterior cruciate ligament reconstructions.

A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee

The aim of this study was to test the hypothesis that the meniscofemoral ligaments (MFLs) of the human knee assist the lateral meniscal function in reducing tibiofemoral contact pressure. Five human cadaveric knee joints were loaded in axial compression in extension using a 4-degree of freedom rig in a universal materials testing machine. Contact pressures pre- and post-sectioning of the MFLs were measured using pressure sensitive film. Sectioning the MFLs increased the contact pressure significantly in the joints for two of the four measures. In addition to their known function in assisting the posterior cruciate ligament (PCL) to resist tibiofemoral posterior drawer, the MFLs also have a significant role in reducing contact stresses in the lateral compartment. Their retention in PCL and meniscal surgery is therefore to be advised.

Critical Shoulder Angle and Acromial Index Do Not Influence 24-Month Functional Outcome After Arthroscopic Rotator Cuff Repair

Background: Recent studies have shown a correlation between scapular geometry and the development of atraumatic rotator cuff tears. However, a paucity of literature is available on the effects of critical shoulder angle (CSA) and acromial index (AI) on functional outcomes after arthroscopic rotator cuff repair. Hypothesis/Purpose: The purpose was to investigate the influence of CSA and AI on 24-month functional outcomes after arthroscopic rotator cuff repair. The hypothesis was that a larger CSA or AI would result in poorer postoperative outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: The study included 147 patients who underwent arthroscopic double-row rotator cuff repair for radiologically documented full-thickness supraspinatus tears. An independent reviewer measured the CSA and AI on preoperative radiographs. These patients were prospectively enrolled and were evaluated preoperatively as well as at 3, 6, 12, and 24 months postoperatively. Functional outcome was assessed with the Constant Shoulder Score (CSS), Oxford Shoulder Score (OSS), and University of California at Los Angeles (UCLA) Shoulder Rating Scale. The patients were first divided based on CSA: (1) ≤35° (control CSA) and (2) >35° (increased CSA); and then based on AI: (1) ≤0.7 and (2) >0.7. The Student unpaired t test, Pearson chi-square test, and Pearson correlation were performed to examine the influence of CSA and AI on postoperative functional outcome scores. Results: At 6 months of follow-up, the CSS, OSS, and UCLA Shoulder Rating Scale were 10 ± 1, 4 ± 2, and 3 ± 1 points poorer in the increased CSA group compared with the control CSA group (P = .005, P = .030, and P = .035, respectively). These scores were not significantly different between both AI groups. By 24 months of follow-up, all outcome scores were comparable between both CSA groups as well as between both AI groups. No significant correlation was found between either CSA or AI when compared with CSS, OSS, or UCLA Shoulder Rating Scale at 24 months of follow-up. Conclusion: CSA and AI do not appear to influence 24-month functional outcomes postoperatively and hence are not contraindications to arthroscopic rotator cuff repair.

MEASUREMENT OF INTRAMENISCAL FORCES AND STRESSES BY TWO DIFFERENT MINIATURE TRANSDUCERS

Injuries to the knee joint are common and often have an adverse impact on a patients quality of life. It is therefore important to understand the load transfer mechanism of the knee, especially with regard to the loading of the menisci in different positions and under different conditions. To date, only contact pressure between joint surfaces and menisci, as well as circumferential strain, have been measured by pressure sensors and strain gauges. Therefore, the aim of this study was to investigate the spread of axial load within the menisci and the effect of the knee flexion angle on the axial load within the menisci. Intrameniscal forces were measured with Fiber Bragg Grating (FBG) sensors and conductive rubber sensors in porcine knee joint specimens. The changes in pressure were measured under different loading conditions. Measurement of the intrameniscal pressure is feasible. Although, there is some existence of variations in readings, some trends can be inferred. From the overall trend, it was observed that higher stress occurs at lateral central and lateral posterior regions. As the occurrences of injuries are mainly at the medial meniscus, this may imply that the level of stress is secondary to the mobility of the meniscus in incidents of injuries. It was found that the posterior meniscofemoral ligament plays a crucial role in the mechanics of the lateral meniscus.

Comparison of a simplified skin pointer device compared with a skeletal marker for knee rotation laxity: A cadaveric study using a rotation-meter

AIM To compare the measurements of knee rotation laxity by non-invasive skin pointer with a knee rotation jig in cadaveric knees against a skeletally mounted marker. METHODS Six pairs of cadaveric legs were mounted on a knee rotation jig. One Kirscher wire was driven into the tibial tubercle as a bone marker and a skin pointer was attached. Rotational forces of 3, 6 and 9 nm applied at 0°, 30°, 45°, 60° and 90° of knee flexion were analysed using the Pearson correlation coefficient and paired t-test. RESULTS Total rotation recorded with the skin pointer significantly correlated with the bone marker at 3 nm at 0° (skin pointer 23.9 ± 26.0° vs bone marker 16.3 ± 17.3°, r = 0.92; P = 0.0), 30° (41.7 ± 15.5° vs 33.1 ± 14.7°, r = 0.63; P = 0.037), 45° (49.0 ± 17.0° vs 40.3 ± 11.2°, r = 0.81; P = 0.002), 60° (45.7 ± 17.5° vs 34.7 ± 9.5°, r = 0.86; P = 0.001) and 90° (29.2 ± 10.9° vs 21.2 ± 6.8°, r = 0.69; P = 0.019) of knee flexion and 6 nm at 0° (51.1 ± 37.7° vs 38.6 ± 30.1°, r = 0.90; P = 0.0), 30° (64.6 ± 21.6° vs 54.3 ± 15.1°, r = 0.73; P = 0.011), 45° (67.7 ± 20.6° vs 55.5 ± 9.5°, r = 0.65; P = 0.029), 60° (62.9 ± 22.4° vs 45.8 ± 13.1°, r = 0.65; P = 0.031) and 90° (43.6 ± 17.6° vs 31.0 ± 6.3°, r = 0.62; P = 0.043) of knee flexion and at 9 nm at 0° (69.7 ± 40.0° vs 55.6 ± 30.6°, r = 0.86; P = 0.001) and 60° (74.5 ± 27.6° vs 57.1 ± 11.5°, r = 0.77; P = 0.006). No statistically significant correlation with 9 nm at 30° (79.2 ± 25.1° vs 66.9 ± 15.4°, r = 0.59; P = 0.055), 45° (80.7 ± 24.7° vs 65.5 ± 11.2°, r = 0.51; P = 0.11) and 90° (54.7 ± 21.1° vs 39.4 ± 8.2°, r = 0.55; P = 0.079). We recognize that 9 nm of torque may be not tolerated in vivo due to pain. Knee rotation was at its maximum at 45° of knee flexion and increased with increasing torque. CONCLUSION The skin pointer and knee rotation jig can be a reliable and simple means of quantifying knee rotational laxity with future clinical application.

Arthroscopic undersurface rotator cuff repair versus conventional arthroscopic double-row rotator cuff repair – Comparable results at 2-year follow-up:

Aim: The aim of our study is to compare the improvement in clinical outcomes after conventional arthroscopic double-row rotator cuff repair and arthroscopic undersurface rotator cuff repair. Method: A consecutive series of 120 patients who underwent arthroscopic rotator cuff repair was analysed. Sixty-one patients underwent conventional double-row rotator cuff repair and 59 patients underwent undersurface rotator cuff repair. Several clinical outcomes, including numerical pain rating scale (NPRS), constant shoulder score (CSS), Oxford shoulder score (OSS) and University of California Los Angeles shoulder score (UCLASS), were prospectively recorded by a trained healthcare professional preoperatively and at 3, 6, 12 and 24 months after surgery. Result: Comparing both groups, there were no differences in age, gender and preoperative NPRS, CSS, OSS and UCLASS. However, the tear size was 0.7 ± 0.2 (95% confidence interval (CI) 0.3–1.1) cm larger in the conventional group (p = 0.002). There was no difference in the improvement of NPRS, CSS, OSS and UCLASS at all time points of follow–up, that is, at 3, 6, 12 and 24 months after surgery. The duration of operation was shorter by 35 ± 3 (95% CI 28–42) min in the undersurface group (p < 0.001). Conclusion: Both arthroscopic undersurface rotator cuff repair and conventional arthroscopic double-row rotator cuff repair showed marked improvements in clinical scores when compared preoperatively, and there was no difference in improvements between both groups. Arthroscopic undersurface rotator cuff repair is a faster technique compared to the conventional arthroscopic double-row rotator cuff repair.

A normative anatomic study of the glenohumeral joint and rotator cuff tendons

Introduction: The purpose of this study is to determine normative values relating to the glenohumeral joint and rotator cuff tendons namely length, width, thickness and footprint of supraspinatus (SS), infraspinatus (IS), teres minor ™ and subscapularis (SC) from 19 specimens. Methods: Rotator cuff tendons and humerus dimensions were measured directly using a digital vernier calliper. In addition, moduli values of rotator cuff tendons were obtained from tensile tests on twelve cadaveric shoulders. The tendon footprints were delineated onto a tracing paper and their dimensions were calculated using digitiser software. The glenoid dimensions were obtained from marking its outline onto a tracing paper and the cavity dimensions from wax moulds. The results were tabulated and statistical analyses, including Students t-test and ANOVA, were performed. Conclusion: The normative anatomic values obtained can be used in finite element modeling, computer simulation, design of implants and surgery.

Effects of Tears and Repairs on Supraspinatus Strain Measurements

Aim: This study aims to simultaneously measure the bursal and articular strains on the supraspinatus and demonstrate the effect of tears and repairs with an intact glenohumeral joint.