Purpose

To (1) report clinical outcomes of arthroscopic interventions of the hip with a minimum of 5-year follow-up utilizing a cohort with femoroacetabular impingement syndrome that did not undergo hip arthroscopy, and (2) determine the influence of hip arthroscopy on the progression of osteoarthritis (OA) of the hip.

Methods and Materials

Patients who (1) presented with hip pain and were diagnosed with FAI and (2) had a minimum follow-up time of 5 years were included. Exclusion criteria were periacetabular osteotomy (PAO) performed ipsilaterally and <5 years of follow-up. A total number of 1565 patients were identified. Hip arthroscopy patients were compared to patients that presented with femoroacetabular impingement but did not undergo hip arthroscopy.

Results

A total of 201 patients were evaluated for inclusion study in the surgical group, with 129 patients (64%), comprising 45 men (35%) and 84 women (85%), eligible based on study criteria. A total of 1364 patients were evaluated for inclusion in the non-surgical group, with 1055 patients (77.3%), comprising 333 men (31.6%) and 722 women (68.4%), eligible based on study criteria. At a mean follow up of 8.4 years, 4.7% of patients of the HA group progressed to THA, compared to 4.5% of the non-operative control group. While most of the HA group showed no (21.7%) or mild signs (Tönnis 1: 65.1%) of OA at follow-up, moderate OA (Tönnis 2) was present in 8.5% of patients compared to 17.4% in the group of non-operative treatment.

Table 1. Radiographic Characteristics of all Patients as Determined by Tönnis Grade

Conclusion

At mid-term follow-up, patients treated with hip arthoroscopy had similar rates of radiographic arthritis and progression to hip arthroplasty compared to non-opeatively reated patients.

Purpose

1) Introduce a novel expiremental model and design to study meniscal healing responses to a variety of treatment options, and 2) to present biomechanical and histological baseline data of the model.

Methods and Materials

Human meniscus tissue was obtained from patients undergoing total knee arthroplasty, according to IRB approved protocols. Standardized human menisci with a central defect filled with autologous meniscus tissue were cultured for up to eight weeks without stimulation. Specimens were cut using biopsy punches, the outer ring with an 8 mm biopsy punch, the inner plug with a 4 mm biopsy punch. Meniscus formation and integrity were analyzed at the defect site through 1) biomechanical testing and 2) histology (Safranin O with Haematoxylin counterstain, Picro Sirius Red) and collagen autofluorescence using confocal microscopy. The biomechanical testing was carried out using a static universal test system. The maximal force required to push out the implant from the meniscus rings (Fmax(insert)) was determined using a cylindrical indenter (diameter 3.8 mm).

Results

A total of 92 samples were tested biomechanically and 21 samples histologically. Both biomechanical maximal push out force, as well as histological analysis showed no significant difference between all time points. No significant healing response was visible in the histological images. These results reflect the limited intrinsic healing properties of the human meniscus.

Figure 1. Force graph of push-out test of a specimen. Force abruptly drops, as soon as inner cylinder is pushed out.

Figure 2. Collagen autofluoresence image of the punch interface of a simulated 7 days old meniscus tear

Conclusion

The present human meniscus punch model represents a robust, reproducible and highly suitable tool for the long-term culture of meniscus tissue, maintaining matrix integrity and homoeostasis. As an alternative to animal studies, this model may closely reflect early stages of meniscus regeneration/healing, allowing the evaluation of promising regenerative treatment regimes.

Purpose

1) Introduce a novel expiremental model and design to induce isolated meniscal tears, 2) to present biomechanical and histological baseline data of the model and 3) to test novel meniscal reconstruction and regeneration methods with the new biomechanical model.

Methods and Materials

A 6 degree-of-freedom robotic arm (HR300 Ultra 2500, Kuka Robotics Corp, Augsburg, Germany) was used in this study. A custom robotic loading profile was created to stress the medial meniscus. The loading profile inludes holding the knee at 60° of flexion while simultaneously applying 1 bodyweight of compression and an internal rotation torque normalized to the specimen’s height and weight. The internal rotation torque was progressively increased from 50% of the normalized value in 10% intervals until significant meniscus damage is present or other knee stabilizing structures fail. The meniscus was visualized and monitored arthroscopically before and after each cycle by a fellowhip-trained orthopedic surgeon.

Results

A total of 3 samples were tested biomechanically. In one specimen a longitudinal tear of the posterior horn of the medial meniscus was induced alongside with an avulsion fracture of the tibial ACL (anterior cruciate ligament) insertion. In a second specimen an isolated radial tear of the meniscal body was induced without concomitant injuries and expanded with subsequent testing. The third specimen, belonging to a 55 year old body donor, sustained a partial tear of the ACL while no meniscal tear was observed.

Conclusion

Our results validate the use of a robotic system as a testing platform for uniquely stressing the meniscus. The robotic system demonstrated high repeatability during manipulation and superior accuracy. The results of this study will provide an effective means for further determination of native knee biomechanical properties and evaluation of the effect of meniscal pathology and surgical interventions during robotically applied motion cycles. The platform showcases promising potential for further specified meniscal testing.