Muscle sparing thoracotomy: a biomechanical analysis confirms preservation of muscle strength but no improvement in wound discomfort

Objectives: This study compares the posterior auscultatory triangle thoracotomy incision (muscle sparing) with full posterolateral thoracotomy (where latissimus dorsi muscle is always cut across its full width), with particular attention to the difference between latissimus dorsi muscle strength, post operative pain and chronic wound related symptoms. Methods: Ten patients who had undergone auscultatory triangle thoracotomy (ATT) at least 1 year previously were matched with ten patients who had undergone posterolateral thoracotomy (PLT). Each pair was matched for age, sex, dominant hand, side of the operation, time since operation and presence or absence of history of previous muscle training. Latissimus dorsi muscle strength was assessed by testing the shoulder adduction strength through an arc of 90–0° using isokinetic technique. Early post-operative pain was assessed indirectly by calculating the analgesic requirement in the first 5 post-operative days. A subjective assessment of chronic post-thoracotomy pain was made using a questionnaire presented to the patients at the time of muscle testing. Variability of the torque curves, recorded as coefficient of variance at the time of muscle strength testing, provided objective measurements of chronic pain. Data were analysed using two sample t-tests. Results: All patients reported at least one chronic post-thoracotomy symptom. There was no significant difference between the two groups in terms of acute or chronic wound pain and other long term wound related symptoms. Shoulder adduction strength was 24% greater in ATT than PLT (95% confidence LIMITS=1–43%, P=0.04). Conclusions: All thoracotomy patients have long term wound related symptoms. This situation is not improved by performing a muscle sparing incision. However thoracotomy through the triangle of auscultation can preserve latissimus dorsi strength which is compromised in a posterolateral thoracotomy incision. We therefore recommend that a muscle sparing thoracotomy be considered for patients where preservation of muscle strength is deemed important, providing the operation is not compromised due to inadequate access.