Lumbar stability following graded unilateral and bilateral facetectomy: A finite element model study.

BACKGROUND: Excision of excessive amount of facet joint during lumbar discectomy or decompression can cause segmental instability of the lumbar spine. This study was performed to assess the segmental instability, facet joint loading and intradiscal pressure following graded lumbar facetectomy. This biomechanical study was performed using a verified and validated L3-S1 finite element model. METHODS: Nine scenarios were analysed. Intact model as control, 30%, 45%, 60% and complete facet joint excision in unilateral and bilateral setting. The effect of progressive graded facetectomy of L4-L5 on the segmental mobility, facet loading and intradiscal pressure was assessed. FINDINGS: In comparison with control 30% excision of the facet joint mainly caused increase in mediolateral mobility. With 45% excision of the facet joint there was increase in both anteroposterior and mediolateral mobility, this was worse in bilateral and unilateral models respectively. This worsened with larger facet excision scenarios. Facet load increased significantly on extension with excision of 45% & 60% unilaterally and 100% bilaterally. Flexion produced rise in intradiscal pressure in all scenarios. INTERPRETATION: The increased spinal mobility, facet loading and intradiscal pressure with more than 30% facetectomy highlights the importance of preserving the facets during decompression thereby safeguarding accelerated degeneration of these segments and iatrogenic segmental instability. The findings from this study could also potentially explain the correlation between spinal instability, disc degeneration and facet joint arthrosis as noted in clinical studies.

Predictors of mortality following conservatively managed fractures of the odontoid in elderly patients.

AIMS: Rates of mortality as high as 25% to 30% have been described following fractures of the odontoid in the elderly population. The aim of this study was to examine whether easily identifiable variables present on admission are associated with mortality. PATIENTS AND METHODS: A consecutive series of 83 elderly patients with a fracture of the odontoid following a low-impact injury was identified retrospectively. Data that were collected included demographics, past medical history and the results of blood tests on admission. Radiological investigations were used to assess the Anderson and D'Alonzo classification and displacement of the fracture. The mean age was 82.9 years (65 to 101). Most patients (66; 79.5%) had a type 2 fracture. An associated neurological deficit was present in 11 (13.3%). All were treated conservatively; 80 (96.4%) with a hard collar and three (3.6%) with halo vest immobilisation. RESULTS: The rate of mortality was 16% (13 patients) at 30 days and 24% (20 patients) at one year after injury. A low serum level of haemoglobin and the presence of a neurological deficit on admission were independent predicators of mortality at 30 days on binary logistic regression analysis. A, low level of haemoglobin, admission from an institution, a neurological deficit and type 3 fractures were independent predictors of mortality at one year. CONCLUSION: We suggest that these easily identifiable predictors present on admission can be used to identify patients at high risk and guide management by a multidisciplinary team. Cite this article: Bone Joint J 2017;99-B:116-21.

Early failure with the Journey-Deuce bicompartmental knee arthroplasty.

The aim of this study was to evaluate the early functional outcome and survivorship of a bicompartmental knee arthroplasty implant (Journey-Deuce) in a cohort of patients with combined medial and patellofemoral degenerative osteoarthritis. Fifteen patients with a mean age of 57 years were followed up prospectively and evaluated with clinical examination, Oxford knee score and radiology imaging. Poor pain scores, concerns about the tibial fixation, early aseptic loosening of the tibial component and a revision rate of 60 % at a minimum follow-up of 54 months are reported. Implantation of this prosthesis was stopped at our institution well before the first revision due to an unfavourable early clinical response. This was further endorsed by an unacceptable revision rate. The outcome of the Journey-Deuce bicompartmental knee replacement was considerably worse than the published outcome of total knee replacement.

Lateral meniscal tear resulting from the femoral cross-pin used for hamstring graft fixation in anterior cruciate ligament reconstruction.

We report a case of lateral meniscal tear resulting from the femoral cross-pin used for hamstring graft fixation in anterior cruciate ligament (ACL) reconstruction. A 29 year old man presented with symptoms of knee pain, catching and locking, 13 months following an ACL reconstruction. Magnetic resonance imaging (MRI) and arthroscopy confirmed the broken femoral cross-pin abutting the lateral meniscus and the resulting meniscal tear. Removal of the broken femoral cross-pin and repair of the lateral meniscal tear resulted in resolution of symptoms. Distal femoral cross-pin fracture and its intra-articular position are postulated as the cause of this lateral meniscal tear. Hence, we recommend a low threshold to investigate with a MRI scan any new symptoms following ACL reconstruction with cross-pin fixation.

Aseptic loosening of the patellar component at the cement-implant interface.

We present four cases of aseptic loosening at the implant-cement interface following patellar resurfacing. All patients initially had good results, but then presented with onset of a new anterior knee pain. The radiographs including flexed lateral and skyline view of the knee were normal in all the cases. After carefully ruling out infection, aseptic loosening at the cement-implant interface was diagnosed on further investigation. Aseptic loosening of the patellar button at the implant-cement interface can be difficult to diagnose with standard knee radiographs. During flexed lateral radiograph of the knee and the skyline view radiograph of the patellofemoral joint, the patella is compressed on the femur and thereby reducing the loose patellar button. This phenomenon has not been previously described. Patients presenting with new onset of knee pain after an initial good results following patellar resurfacing require further investigation to exclude loosening at the cement-implant interface as plain radiographs can be misleading.

Bilateral total knee replacement in a congenital amputee with bilateral fibular deficiency.

We present the first ever reported case of bilateral total knee replacements in a congenital amputee with bilateral fibular deficiency. A 60 year old woman with bilateral fibular hemimelia presented with advanced osteoarthritis in both her knees for which bilateral total knee replacements was performed. The left knee replacement was followed up at 12 months and the right knee at 7 years. Oxford knee scores improved from 14 to 40 for the left knee and were 37 for the right knee. She was able to walk independently to a distance beyond 400 m. Modification in the surgical procedure and postoperative rehabilitation is discussed. Mid-term follow-up of 7 years reaffirms total knee replacement as a viable option for below knee amputees with knee osteoarthritis.