Session III - Rehabilitation

The Effects of Periosteal Elevation on Osteotomy Healing in a Rabbit Tibial Model

Paul Watson, MD; Douglas C. Fredericks, BS; James V. Nepola, MD, Bone Healing Research Laboratory, University of Iowa College of Medicine, Iowa City, IA

Purpose: To evaluate osteotomy healing following elevation or excision of the periosteum around an osteotomy site in a rabbit tibial model.

Methods: Thirty-six rabbits were entered into the study. After sterile preparation, a four-pin external fixator (M120, Orthofix, Verona, Italy) was placed medially on the left tibia of each rabbit. A hole was drilled through the two muscle bodies on the anteromedial side of the tibia below the fibular synarthrosis with a 1.7-millimeter drill bit. A 1.3-millimeter drill bit was then used to drill through the same hole on all aspects on the endosteal cortex to create a fracture. In the control group (Group I, n=12) the periosteum was left intact with the surrounding bone. In Group II (n=12) a freer was used to completely elevate the periosteum along the diaphysis between the two inner most pins. The periosteum and muscle were then sutured in a routine surgical manner. In Group III (n=12), the periosteum was excised from the area between the two pins and the muscle sutured back in place. Skin was closed in a routine surgical manner in all groups. Anteroposterior and medial lateral radiographs were taken weekly until the animals were sacrificed at 21 days. Eight tibiae from each group underwent torsional testing to failure. The remaining four tibia from each group were designated for decalcified histology.

Results: Radiographs showed callus at the fracture site on all cortices in Group I. Defined peaks of callus were noticed on the diaphysis at the fracture site. In Group II, bridging periosteal callus appeared in 8/8 tibiae with callus extending from pin to pin. Callus was seen on the posterolateral aspect of the diaphysis in Group III. No callus was seen on the anteromedial side of the diaphysis in 6/7 tibiae in this group. Histology: Intact periosteum were evident in Group I and Group II. In Group III small pieces of periosteum was seen on the posterior side of the diaphysis but were not evident elsewhere.

Torsional Testing: The excised periosteum group (mean 1.61 Nm) was significantly different from the control (mean 2.28 Nm) and elevated (2.89 Nm) groups, p=0.013 and p<0.05 respectively. The elevated periosteum group had significantly greater torsional strength than the control group, p=0.02. All tibiae tested were significantly different from historical normal intact controls (mean 3.75 Nm), p<0.05.

Discussion: Previous studies have demonstrated that periosteal stripping (excision) delays fracture healing. To our knowledge no previous study has assessed the effects of periosteal elevation on fracture healing. Elevation of the periosteum, in our study, appears to increase callus area. This increased area of callus correlates with torsion strength of the tibiae. Excision of the periosteum decreases callus formation and torsional strength in this model.

Study Limitations: This study had only one time period and did not determine if these tibiae reach normal torsional strength.

Conclussion: Periosteal preservation is essential for osteotomy repair. Elevation of the periosteum in this osteotomy model increased callus formation and torsional strength, whereas excision of the periosteum decreased callus formation and torsional strength.