Objectives

Osteochondral injuries, if not treated adequately, often lead to severe osteoarthritis. Possible treatment options include refixation of the fragment or replacement therapies such as Pridie drilling, microfracture or osteochondral grafts, all of which have certain disadvantages. Only refixation of the fragment can produce a smooth and resilient joint surface. The aim of this study was the evaluation of an ultrasound-activated bioresorbable pin for the refixation of osteochondral fragments under physiological conditions.

Bone shape variability within a specific population has been seldom investigated and used to optimize implant design. There is insufficient anatomical fitting of the existing prebend periarticular plates for the distal fibula. We developed a methodology for design of orthopaedic implants that fit a maximum percentage of the target population, both in terms of geometry and biomechanical stability. In co-operation with an implant manufacturer and different academic institutions, a virtual bone database has been developed that contains anatomical data of more than 1000 CT datasets with the implemented possibility to generate idealized implant fits for different anatomical sites. This program (Stryker Virtual Bone Database (VBD) is able to generate statistical anatomical shapes for different populations like age groups or ethnical groups. Based on this, an implant for the distal fibula has been developed (VariAx Distal Lateral Fibula Locking Plate) for distal fibula fracture treatment. Aim of this study was to develop and validate an implant that is optimized for the specific anatomical area. It should be precontoured and still fit to the majority of patients sustaining a distal fibular fracture. Another objective was to create a distally tapered design as there is less soft tissue cover in that anatomic area.

Introduction

The degeneration of the adjacent segment in lumbar spine with spondylodesis is well known, though the exact incidence and the mechanism is not clear. Several implants with semi rigid or dynamic behavior are available to reduce the biomechanical loads and to prevent an adjacent segment disease (ASD). Randomized controlled trials are not published. We investigated the biomechanical influence of dynamic and semi rigid implants on the adjacent segment in cadaver lumbar spine with monosegmental fusion (MF).

In an interdisciplinary project involving electronic engineers and clinicians, a telemetric system was developed to measure the bending load in a titanium internal femoral fixator. As this was a new device, the main question posed was: what clinically relevant information could be drawn from its application? As a first clinical investigation, 27 patients (24 men, three women) with a mean age of 38.4 years (19 to 66) with femoral nonunions were treated using the system. The mean duration of the nonunion was 15.4 months (5 to 69). The elasticity of the plate-callus system was measured telemetrically until union. Conventional radiographs and a CT scan at 12 weeks were performed routinely, and healing was staged according to the CT scans. All nonunions healed at a mean of 21.5 weeks (13 to 37). Well before any radiological signs of healing could be detected, a substantial decrease in elasticity was recorded. The relative elasticity decreased to 50% at a mean of 7.8 weeks (3.5 to 13) and to 10% at a mean of 19.3 weeks (4.5 to 37). At 12 weeks the mean relative elasticity was 28.1% (0% to 56%). The relative elasticity was significantly different between the different healing stages as determined by the CT scans.

Incorporating load measuring electronics into implants is a promising option for the assessment of bone healing. Future application might lead to a reduction in the need for exposure to ionising radiation to monitor fracture healing.

Implants with multidirectional locked screws have theoretical advantages in the treatment of periprosthetic fractures. In osteoporotic bone those locked plate systems with multidirectional applicable screws give a high stability. With the possibility of fixing screws in various angles, a rigid fixation in the presence of a prosthetic implant can be achieved. We concluded a retrospective study of a consecutive series of the outcome of Vancouver B1 and C femoral injuries using two specific locked implants (Straight and wave plate).

From June 1996 to December 2004 we treated 58 patients with a periprosthetic fracture of the femur with a locked plate. The mean age at the index procedure was 72.4 years, 40 patients were female (69%). In 32 cases (55.2%) we saw a hip endoprosthesis, in 21 cases (36.2%) a knee endoprosthesis and in 5 cases both (8.6%). Outcome measures were intra- and postoperative complications, bony union, degree of mobility and social status, Barthel mobility index and “stand up and go” test.

Union occurred in 56 cases (96.5%) after the index procedure. Twice the implant failed, we saw 4 general complications. The mean duration until full weight bearing status in these patients was 8.6 weeks.

At follow up 46 patients (78%) had maintained the same social status as before the fracture. Regarding the mobility status 52 patients (89%) had regained their previous level, 4 patients walking without aid before now required a cane and two patients a walking frame. The mean Barthel Index was 85 points of possible 100 and improved from 35 points at point of beginning of the rehabilitation. The mean stand-up& go time was measured as 22 seconds.

Conclusion: Overall failure rates of osteosynthesis after periprosthetic fractures of up to 35% are reported (20). With 3.5% implant related failures and 7% general complications, the presented Methods: achieve bony union and mobility in a high percentage of cases.

Introduction: In the last ten years there is a clear favour toward internal fixation. We evaluated the technique and the clinical long term results of external fixation in a triangular frame.

Patients and Methods: From 1994 to 2001 a consecutive series of 95 patients with end stage arthritis of the ankle joint were treated. Retrospectively the case notes were evaluated. Mean age at the index procedure was 45.4 years (18–82), 67 patients were male (70.5%). In all cases the arthritic deformity was due to a posttraumatic condition. The index procedure took place on average 129 months (6–516 months) after trauma. Preoperatively 43 patients had a relevant mal-alignment. In 41 patients the range of motion (ROM) was decreased with a remaining ROM of < 20°, in further 37 cases the remaining ROM was < 10° ROM. Via a bilateral approach the malleoli and the joint surfaces were resected. An AO fixator was applied with four Steinmann-nails inserted. Follow up examination at mean 4.4 years included a standardised questionnaire and a clinical examination including the criteria of the AOFAS-Score and radiographs.

Results: In all cases the index procedure was possible although in 2 cases soft tissue contracture meant that a pes equinus position of approximately 15° was required. After mean 12.3 (8–16) weeks radiographs confirmed satisfactory union and the fixator was removed. There were no cases of DVT or PE detected in the postoperative period. In 9 cases (10.1%) we saw a reversible irritation of the dorsal cutaneous nerve. In 18 cases a pin tract infection developed (20.2%) which healed under conservative measures. In one case (1.1%) a bony infection around a pin site developed, one patient suffered a fracture of the tibia at the site of the former proximal tibial pin site due to a minor trauma. In 4 patients a non-union of the ankle arthrodesis developed (4.5%). The mean AOFAS score improved from 20.8 (Std. dev.16.2) to 69.3 at F/U (Std.dev. 21.5, p = 0,004–30, T-test). The largest improvements were found regarding to pain and walking distance. Whilst preoperatively only one patient had mild pain, at follow up 54 patients had no or only mild pain. The maximal walking distance improved from mean 675 metres to mean 3245 m (T-test, p < 0,025 –18). Analysis of the insurance status showed patients that patients insured under a workers injury compensation scheme had a mean score of 63.6 compared to 75.1 for the remaining (T-test, p=0,027).

Discussion: Non-union rates and clinical results of arthrodesis by triangular external fixation of the ankle joint do not differ to internal fixation

Methods: The complication rate and the reduced patient comfort reserve this method mainly for infected arthritis and complicated soft tissue situations.