The evaluation of two methods for the placement of the tibial component of total knee arthroplasties in obese patients

Between December 2004 and October 2008 we studied 38 obese patients who underwent cemented total knee arthroplasty (using the rotating platform tibial tray) due to medial compartment osteoarthritis and consequent varus deformity. All patients had a body mass index (BMI)> 40. Functional outcome was assessed using the Knee Society Score (KSS). The study was based on the comparison between extramedullary (group A) and intramedullary (group B) instrumentation systems for the placement of the tibial prosthesis. The main endpoint was the immediate post-operative knee joint alignment.

There were 10 male and 28 female patients. The average follow-up period was 13.8 months (minimum follow-up of 6 months). There were 22 patients in group A whereas 16 patients comprised group B. In 5 of the 22 patients in group A there was an average varus malalignment of 40 and a mean KSS of 71.5 at the time of the latest follow-up visit. In the rest of patients of both groups there was a valgus alignment between 0 and 70 and a mean KSS of 86.4 respectively

Our experience suggests that the intramedullary instrumentation technique for the placement of the tibial component offers a more favourable post-operative alignment as well as better functional outcome in obese patients.

The evaluation of early results of combined percutaneous pedicle screw fixation and kyphoplasty for the management of thoraco-lumbar burst fractures

Between October 2008 and April 2009, 9 patients with thoracolumbar burst fractures underwent percutaneous short-segment pedicle screw fixation and augmentation kyphoplasty with calcium phosphate cement. All patients were selected according to the type of fracture (unstable type A3 fractures based on the Magerl classification) the absence of neurological signs and an intact posterior longitudinal ligament on the pre-operative MRI scan. Patient demographics, co-morbidities and complications were recorded. The main endpoints included Cobb angle correction, vertebral body height restoration and the length of hospital stay.

There were 3 male and 6 female patients with an average age of 43.6 years. The average follow-up was 2.4 months. The mean kyphotic angulation improved from 18.40 pre-operatively to 6, 80 post-operatively. The loss of vertebral body height improved from a mean of 38.7 % pre-operatively to 12.1 % post-operatively. The average duration of surgery was 40 minutes with insignificant blood loss. There were no post-operative complications. The average length of hospital stay was 3.2 days.

The combination of percutaneous short-segment pedicle screw fixation supplemented by balloon kypho-plasty for the management of thoracolumbar burst fractures with no neurological deficit offers correction of the normal thoracolumbar anatomy as well as augmentation of the anterior load-bearing column, using a minimally invasive technique. The early results are promising

The evaluation of results following posterior decompression and fusion for the management of cervical spondylotic myelopathy

Between July 2006 and May 2008, 68 patients with cervical myelopathy underwent posterior decompression with laminectomies and pedicle screw fixation of the cervical spine. All patients were selected based on the presence of multi-level degenerative disease and the correction of cervical lordosis on the pre-operative dynamic radiographs. Patient demographics, co-morbidities and post-operative complications were recorded and analysed. Functional outcome was assessed by using the Japanese Orthopaedic Association (JOA) score.

There were 37 male and 31 female patients with an average age 67.4 years. The average follow up period was 18 months. The mean pre-operative JOA score was 8.7, whereas the mean post-operative score was 12.1 on the latest follow-up visit. 9 patients had unsatisfactory clinical results and consequently underwent anterior procedures with significant improvement. Complications included 1 epidural haematoma, 2 superficial infections and 4 cases of myofascial pain. In three cases there was mild dysfunction of the C5 nerve root which resolved spontaneously with conservative measures.

In the present series of patients posterior decompression with laminectomies is an effective method for the management of cervical spondylotic myelopathy.

Background: During cemented hip arthroplasty revision removal of all the old cement mantle is a time staking process with multiple disadvantages. In some selected patients cementing revision stem into the old mantle is regarded as a highly attractive option. Contradictory evidence exists whether bond between two cement layers is strong enough, especially in the presence of interfering fluids.

Aim: analysis of the shearing strength of the interface between two layers of polymethylmethacrylate cement in the presence of fluid.

Methods: Cylindrical blocks of polymethylmethacrylate cement represented primary cement mantle. Its flat surface was machined to reproduce smooth old cement mantle surface comparable with that after removal of a highly polished stem (Ra=200nm). A second block was cast against the first and their junction represented the investigated interface. The influence of fluid was examined by injecting liquid onto the ‘primary’ surface prior to casting. Water or 2% water solution of carboxy-methyllcellulose (representing bone marrow viscosity of 400mPas) were used in two volumes: 0.02ml/cm2 (small) or 0.4ml/cm2 (large - surface submerged).

6 variants (control monoblock, dry surface, surface stained with small or large volume of water or highly viscous fluid) containing 7 repeats were exposed to a single shearing stress to failure at the speed of 1mm/min (Autograph AGS, Shimadzu, Japan).

Results were analyzed using 1-way ANOVA with post-hoc analysis (equal N HSD) and power calculations.

Results: Large volume of viscous fluid prevented bonding completely in two cases and significantly weakened the other samples showing mean failure stress of 5.53 MPa (95%CI:1.33–9.73 MPa). This was significantly lower compared with control monoblock (19.8–95% CI: 17.8–21.9 MPa), dry surface variant (16.9–95% CI: 15.9–18.0 MPa) and that stained with small amount of high viscosity fluid (16.01–95% CI: 15.12–17.0 MPa). Interestingly, presence of a large volume of low viscosity fluid (water) did not significantly reduce resistance to shear stress (17.05 – 95% CI:15.67–18.43 MPa).

Similar relations were observed when strain at failure and toughness were analyzed.

Conclusions: In all but large volume of viscous fluid variants, the failure occurred away from the interface between two cement layers. Large amount of viscous fluid weakened significantly this interface. If such a viscous fluid can be eliminated by copious water irrigation it is likely that strength of the cement-cement bond will be maintained. In the presence of low viscosity fluids (water, blood) careful use of gun technique is likely to allow for their escape as the cement is advanced within the femoral or the old mantle canal leading to a satisfactory bond. Our observations suggest that cement-in-cement technique seems to be biomechanically acceptable.

Introduction: Ever since the coding has been introduced in the NHS there has been lot of debate whether the trust is being paid accurately. There is no data available which compares the coding done by the surgeon and the one done by the coding department.

Material and Methods: A prospective study was done on 305 patients in an elective orthopedic hospital over a period of one month. All operations were coded separately by the operating surgeon and the coding department. The procedures included all upper and lower limb procedures other than elective hand, spine and paediatric procedures. The results were compared by an independent assessor in line with the national guidelines and the information originally available to clinical coders.

Results: The results showed a marked difference in reimbursement cost of complex procedures, revisions and co-morbidities as coded by the surgeon who took into consideration additional top ups which were available and these were often missed by the coding department. There was no difference in the primary hip and knee arthroplasty.

Conclusion: There is an increased need for correct coding as this can result in potential income consequences by applied tariffs. With the introduction of acute phase tariffs and marked difference in reimbursement to the trust if correct codes are not applied, there is an increased need for awareness for the coding and the top-ups available for complex procedures.

We describe a patient in whom an initially intact sciatic nerve became rapidly encased in heterotopic bone formed in the abductor compartment after reconstruction of the posterior wall of the acetabulum following fracture. Prompt excision and neural release followed by irradiation and administration of indometacin resulted in a full neurological recovery and no recurrence 27 months later.

Pedicle screw fixation has become the norm for the surgical correction of adolescent idiopathic scoliosis (AIS), with much biomechanical research into different types of rod screw constructs. The senior authors have experience using a monoaxial screw only construct in the correction of AIS since 2003 and the polyaxial screw only construct since 2005.

We retrospectively reviewed our experience in the first ten patients with AIS using the polyaxial system and compared this against 18 patients who had been corrected using the monoaxial system. Table I shows our results, expressed as mean and ranges or means ± SD for the main thoracic and lumbar curves.

Our early results show that the polyaxial system produces similar correction of both the thoracic and lumbar curves as compared to the monoaxial system in the immediate post-operative period. Though the absolute values for the lumbar curves differ between the two groups the percentage correction shows no statistical difference.