Abstract
Dear Editor,
The article by Kuhn et al. 1 titled ‘blood flow to the metatarsal head after chevron bunionectomy’ was quite interesting, informative, and innovative. It would be helpful if the authors could clarify the following points:
The article states that the maximal insult to blood flow was recorded after the medial capsulotomy. Was this observation made after a simple capsulotomy or were the recordings made after mobilization of the dorsal and volar capsules in preparation for the osteotomy? If not, do the authors have any explanation for the decrease in blood flow considering that the medial surface has not been identified as a significant source of blood supply to the metatarsal head? 2,3
The 45% reduction in blood flow after the medial capsulotomy and further 13% reductions each with a lateral release and the osteotomy are calculated from the same initial base line reading, which could be considered flawed. If the calculations are redone with the base line reading taken as the blood flow before each step of the procedure, then the adductor tenotomy and the osteotomy would show a decrease in blood flow of 24% and 31%, respectively. This could be more significant than the 45% fall with the medial capsulotomy, considering the lower blood flow levels each of the next two steps start with.
The authors state that the tip of the probe was placed at a depth of 5 mm in the metatarsal head. Was this from the dorsal or plantar surface? MRI studies evaluating blood flow after Austin osteotomies have shown avascular areas predominantly in the dorsal cancellous area of the metatarsal head. 4 . Was this taken into account?
The authors by their exclusion criteria have excluded all patients who could already have a decreased blood flow to the foot and who would hence be candidates for a critical reduction in blood flow from the procedure, leading to an avascular necrosis. Do they practice the same exclusion criteria in their regular practice? Could this be the reason for their zero incidence of avascular necrosis over 10 years or could it be a case of statistical outlying?
Mr Joby Jacob George Malal
Senior SHO in Orthopaedics,
Glasgow Royal Infirmary,
84 Castle street,
Glasgow,
United Kingdom,
G4 0SF.
Mr Bobin Varghese
Senior SHO in Orthopaedics,
Leeds General Infirmary,
Great George street,
Leeds,
United Kingdom,
LS1 3EX.
Dear Editor,
We thank the writer for the constructive comments on our article and wish to address each question posed. We have continued to receive e-mails and support for our research. The first question posed was related to the first reading after medial capsulotomy. We routinely perform a medial capsulotomy with judicious mobilization of the dorsal and volar capsules. Our goal is to mobilize only enough capsule to allow for shifting the metatarsal head after bunionectomy. In the design of the study, we recorded the reading after medial capsulotomy with dorsal and volar mobilizations.
The second question posed was a comment on the method by which reductions in blood flow were calculated. We measured insults to blood flow from the baseline recording in order to keep standardized the comparison point. An alternative to measure each change relative to the prior recording requires deviation from the procedural steps and our standardized bunionectomy procedure.
The writer asked for clarification on the location of the probe in the metatarsal head. The probe was placed centrally in the metatarsal head to avoid bias from changes in extreme dorsal or volar blood flow. This avoids bias regarding a relatively avascular dorsal region and measures a blood flow across the metatarsal head.
The final inquiry was a question of the exclusion criteria for the study. We chose the exclusion criteria carefully to avoid bias in our patient population. Our selection criteria for patients outside the study receiving a chevron bunionectomy are not as stringent. We thought the stringent criteria used in the study were necessary to avoid potential confounders in the study. Thus, this has no obvious effect on our clinical results without incidence of avascular necrosis.
Michael A. Kuhn, M.D
New England Baptist Hospital
Orthopaedics
125 Parker Hill Ave
Boston, MA 02120