Role of the anterior intermeniscal ligament in tibiofemoral contact mechanics during axial joint loading.

The anterior intermeniscal ligament (AIML) is an anatomically distinct structure that connects the anterior horns of the medial and lateral menisci. We hypothesized that both menisci work together as a unit in converting axial joint loading into circumferential hoop stresses, due to intermeniscal attachments. Therefore, loss of the AIML could lead to increased tibiofemoral contact stress and predispose to arthritic change. In this cadaveric study, we compared tibiofemoral contact pressures on axial loading, before and after sectioning of the AIML. Five fresh frozen human cadaveric knees were mounted on a linear x-y motion table and loaded in extension under axial compression of 1800N (about 2.5 times body weight for a 70kg individual), using a materials testing machine. Tibiofemoral contact pressures before and after sectioning of the AIML were measured using resistive pressure sensors. Contrary to our hypothesis, sectioning of the AIML produced no statistically significant increase in mean contact pressure, peak contact pressure or change in contact area, in either the medial or lateral compartment of the knees. This implies that the menisci work independently in converting axial loads into circumferential hoop stresses, and is probably due to their individual root attachments to the tibia. Based on this study, inadvertent sectioning of the AIML during knee surgery, e.g., arthroscopy, anterograde tibia nailing, anterior cruciate ligament reconstruction, meniscus transplantation and unicondylar knee replacement, is functionally insignificant.

Two-year outcomes of transforaminal lumbar interbody fusion.

PURPOSE: To evaluate the outcomes, fusion rates, complications, and adjacent segment degeneration associated with transforaminal lumbar interbody fusion (TLIF). METHODS: 32 men and 80 women aged 15 to 85 (mean, 57) years underwent 141 fusions (84 one-level, 27 2-level, and one 3-level) and were followed up for 24 to 76 (mean, 33) months. 92% of the patients had degenerative lumbar disease, 15 of whom had had previous lumbar surgery. Radiographic and clinical outcomes were assessed at 2 years. The short-form 36 (SF-36) health survey, visual analogue scale (VAS) for pain, and the modified North American Spine Society (NASS) Low Back Pain Outcome Instrument were used. RESULTS: Of the 141 levels fused, 110 (78%) were fused with remodelling and trabeculae (grade I), and 31 (22%) had intact grafts but were not fully incorporated (grade II). No patient had pseudoarthroses (grade III or IV). For one-level fusions, poorer radiological fusion grades correlated with higher VAS scores for pain (p<0.01). All components of the SF-36, the VAS scores for pain, and the NASS scores improved significantly after TLIF (p<0.01), except for general health in the SF-36 (p=0.59). Improvement from postoperative 6 months to 2 years was not significant, except for physical function (p<0.01) and role function (physical) [p=0.01] in the SF-36. Two years after TLIF, 50% of the patients reported returning to full function, whereas 72% were satisfied. 26 (23%) of the patients had adjacent segment degeneration, but only 4 of them were symptomatic. CONCLUSION: TLIF is a safe and effective treatment for degenerative lumbar diseases.

Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion.

STUDY DESIGN: Prospective study. OBJECTIVE: Comparison of clinical and radiologic outcomes of minimally invasive (MIS) versus Open transforaminal lumbar interbody fusion (TLIF). SUMMARY OF BACKGROUND DATA: Open TLIF has been performed for many years with good results. MIS TLIF techniques have recently been introduced with the aim of smaller wounds and faster recovery. METHODS: From 2004-2006, 29 MIS TLIF were matched paired with 29 Open TLIF. Patient demographics and operative data were collected. Clinical assessment in terms of North American Spine Society, Oswestry Disability Index, Short Form-36, and Visual Analogue scores were performed before surgery, 6 months and 2 years after surgery. Fusion rates based on Bridwell grading were assessed at 2 years. RESULTS: The mean age for MIS and Open procedures were 54.1 and 52.5 years, respectively. There were 24 females and 5 males in both groups. Fluoroscopic time (MIS: 105.5 seconds, Open: 35.2 seconds, P < 0.05) and operative time (MIS: 216.4 minutes, Open: 170.5 minutes, P < 0.05) were longer in MIS cases. There was less blood loss in MIS (150 mL) versus Open (681 mL) procedures (P < 0.05). The total morphine used for MIS cases (17.4 mg) was less compared to Open (35.7 mg, P < 0.05). MIS (4 days) patients have shorter hospitalization compared to Open (6.7 days, P < 0.05). Both MIS and Open groups showed significant improvement in Oswestry Disability Index (P < 0.05), back pain and lower limb symptoms (North American Spine Society and Visual Analogue scores, P < 0.05), and Quality of Life scores (Short Form-36, P < 0.05) at 6 months and 2 years, but there was no significant difference between the 2 groups. Eighty percent of MIS and 86.7% of Open TLIF levels achieved grade 1 fusion (P > 0.05). CONCLUSION: MIS TLIF has similar good long-term clinical outcomes and high fusion rates of Open TLIF with the additional benefits of less initial postoperative pain, early rehabilitation, shorter hospitalization, and fewer complications.