Biomedical subjects

Simon Sporrer

Publications and source records attributed to Simon Sporrer.

3 recordsLinked to original sources

PubMed2003

Does partial weight bearing unload a healing bone in external ring fixation?

BACKGROUND: Partial weight bearing is thought to unload and protect the healing bone. Until now, there has been no objective method of assessing the amount of weight placed on the healing zone by the patient. The goal of this study was to determine the effects of partial weight bearing on the loading of the healing bone in tibial osteotomies. MATERIALS AND METHODS: Six patients with complex tibial osteotomies, stabilized with Ilizarov ring fixator constructs, took part in this study. Three-dimensional interfragmentary movements were measured with reflective markers that were attached to the Schanz screws of the fixator. Patients were asked to rest, to co-contract the musculi gastrocnemii, to stand up, to walk slowly and to load partially the affected limb with 20 kg of weight. RESULTS: Compared with co-contraction, ground reaction forces of partial weight bearing, standing up and walking were significantly increased (P<0.05). The interfragmentary movements during partial weight bearing were, however, comparable in partial weight bearing, standing up and walking (P>>0.05). CONCLUSIONS: Partial weight bearing did not unload the defect zone. No direct relationship between interfragmentary movement magnitudes and ground reaction forces was identified. Therefore, the concept of partial weight bearing cannot reliably reduce loading of a healing zone. It may, however, help to prevent patients from undergoing critical situations, such as stumbling, by increasing their general awareness.

Adult↗

PubMed2003

Interfragmentary movements in the early phase of healing in distraction and correction osteotomies stabilized with ring fixators.

BACKGROUND: Experimental analyses have demonstrated the impact of mechanical conditions on bone healing. In critical clinical cases the mechanical conditions may be even more demanding than those in experimental studies. This study set out to examine the gap movements in distraction and correction osteotomies and to determine the suitability of initial fixation. PATIENTS AND METHODS: Interfragmentary movements, ground reaction forces, and stability (ground reaction force divided by interfragmentary movement) were measured in 18 patients with tibial osteotomies stabilized by Ilizarov hybrid constructs until either bone union or conversion to internal fixation occurred (9 distraction treatments, 9 correction osteotomies). Consolidation was determined by clinical evaluation and standard radiographic techniques. RESULTS: In both groups cocontraction led to gap movements comparable to level walking. Although the in vitro stiffness was slightly increased in the correction constructs, the interfragmentary movement in vivo was initially comparable between the groups. Patients undergoing distraction returned later to full weight bearing than patients undergoing correction treatment. In the correction group the stability increased with treatment time, while in the distraction group the stability remained relatively small. CONCLUSIONS: The in vivo mechanical conditions in challenging clinical cases appear far more demanding than those in experimental studies. In distraction, mechanical conditions at the defect appear to be more critical than during correction osteosynthesis. According to the persistence of shear motion, even after 80 days of treatment, it may from the clinical point of view be important to maintain interfragmentary compression during the whole healing process and thereby reduce shear.

Adult↗

PubMed2002

Interfragmentary motion in tibial osteotomies stabilized with ring fixators.

Relative movement of bone fragments affects healing processes. In vivo data exist for patients with reduced transverse fractures only. The gap movements that occur under more complex conditions such as in tibial osteotomies, however, are unknown. The goal of this study was to determine the initial gap movements in tibial correction osteotomies, to monitor movements during the early healing period, and to determine the suitability of initial fixation stability in relation to daily activities. The interfragmentary movements were measured in six patients with correction osteotomies stabilized by Ilizarov ring fixator constructs until union or until conversion to internal fixation. Consolidation was determined by clinical evaluation and standard radiographic techniques. Co-contraction led to gap movements comparable with level walking or standing. Shear generally exceeded axial compression. Although ground reactions and fixation stiffness were comparable with those reported for reduced fractures, movement magnitudes generally were larger than 2 mm. The shear movement component reflected the nature of the mechanical conditions at the bone gap. In a direct comparison with data from animal experiments, the local mechanical environment at the bone gap seemed unstable rather than overly stable. The method introduced in this study opens the perspective of adjusting osteosynthesis stability to the specific needs of each patient.

Adult↗